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In this study, a set of 10 positional indolocarbazole (ICz) isomers substituted with dicyanomethylene groups connected via para or meta positions are computationally investigated with the aim of exploring the efficiency of structural isomerism and substitution position in controlling their optical and electronic properties. Unrestricted density functional theory (DFT), a spin-flip time-dependent DFT approach, and the multireference CASSCF/NEVPT2 method have been applied to correlate the diradical character with the energetic trends (i.e., singlet–triplet energy gaps). In addition, the nucleus-independent chemical shift together with ACID plots and Raman intensity calculations were used to strengthen the relationship between the diradical character and (anti)aromaticity. Our study reveals that the substitution pattern and structural isomerism represent a very effective way to tune the diradical properties in ICz-based systems with meta-substituted systems with a V-shaped structure displaying the largest diradical character. Thus, this work contributes to the elucidation of the challenging chemical reactivity and physical properties of diradicaloid systems, guiding experimental chemists to produce new molecules with desirable properties. Funding for open access charge: Univesidad de Málaga/CBUA. The work at the University of Málaga was funded by the MICINN (PID2019-110305GB-I00) and Junta de Andalucía (UMA18-FEDERJA-080, P09FQM-4708, and P18-FR-4559) projects. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the SCBI (Supercomputing and Bioinformatics) centre of the University of Málaga. The work at the University of Alicante was supported by the MICINN (PID2019-106114GB-I00). The work at the University of Bologna was supported by University of Bologna (RFO) funds.

A new design paradigm for the production of low band gap polymers is reported, in which an ambipolar unit exhibiting both donor and acceptor properties is combined with a conventional acceptor. As initial examples of this approach, the synthesis of two alternating copolymers of thieno[3,4

This work describes the synthesis and properties of a dicyanomethylene‐substituted indolo[3,2‐b]carbazole diradical ICz‐CN. This quinoidal system dimerises almost completely to (ICz‐CN)2, which contains two long C(sp3)−C(sp3) σ‐bonds between the dicyanomethylene units. The minor open‐shell ICz‐CN component in the solid‐state mixture was identified by EPR spectroscopy. Cyclic voltammetry and UV–visible spectroelectrochemical data, as well as comparison with reference monomer ICz‐Br reveal that the nature of the one‐electron oxidation of (ICz‐CN)2 at ambient temperature and ICz‐CN at elevated temperature is very similar in all these compounds due to the prevailing localization of their HOMO on the ICz backbone. The peculiar cathodic behaviour reflects the co‐existence of (ICz‐CN)2 and ICz‐CN. The involvement of the dicyanomethylene groups stabilizes the close‐lying LUMO and LUMO+1 of (ICz‐CN)2 and especially ICz‐CN compared to ICz‐Br, resulting in a distinctive cathodic response at low overpotentials. Differently from neutral ICz‐CN, its radical anion and dianion are remarkably stable under ambient conditions. The UV/Vis(–NIR) electronic transitions in parent (ICz‐CN)2 and ICz‐CN and their different redox forms have been assigned convincingly with the aid of TD‐DFT calculations. The σ‐bond in neutral (ICz‐CN)2 is cleaved in solution and in the solid‐state upon soft external stimuli (temperature, pressure), showing a strong chromism from light yellow to blue–green. Notably, in the solid state, the monomeric diradical species is predominantly formed under high hydrostatic pressure (>1 GPa). The work at the University of Málaga was funded by the MICINN (PID2019-110305GB-I00, PID2019-104293GB-I00 and PCI2019-111825-2), Instituto de Salud Carlos III (ISCIII) (RETIC ARADYAL, RD16/0006/0012) and Junta de Andalucía (UMAFEDERJA-080, UMA-FEDERJA-007 and P09FQM-4708) projects. S.R.G. also thanks the Ayuda para la incorporación de doctores of the University of Malaga. The work at the University of Alicante was supported by the MICINN (PID2019-106114GB-I00) and Generalitat Valenciana (AICO/2018/175) projects. The work at SIOC was supported by National Natural Science Foundation of China (grants no. 21875279 and 21790362). The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the SCBI (Supercomputing and Bioinformatics) center of the University of Malaga. The spectro-electrochemical studies (R.N.) were fully funded by Spectroelectrochemistry Reading (a spinout company of the University of Reading). M.P.-A. would like to acknowledge the support of the European Research Council (ERC) Grant “Hecate”, reference no. 695527, held by Prof. Graeme Ackland. This work has been also supported by MCIU/MINECO through the projects CTQ2013-48252-P, CTQ2015-67755-C02-01-R and PGC2018-094814-B-C21.

We report the synthesis and characterization of a novel series of push-pull chromophores bearing 1D linear and β-branched thiophenes as π-conjugated spacers between a 2,2,4,7-tetramethyl-1,2,3,4-tetrahydroquinoline electron donor unit and dicyano- and tricyanovinylene electron acceptor groups. The effect of the introduction of β-thiophenes on the linear and nonlinear (NLO) optical properties as well as electrochemical and thermal data is studied in detail by performing a comparative study between the branched and 1D linear systems. In addition, a parallel DFT computational study is used to evaluate structure-property relationships. The non-linear optical behavior of the molecules both in solution and in solid state as electro-optic (EO) films using a guest-host approach shows very promising performance for electro-optic applications with high molecular first hyperpolarizabilities (μβ) of 4840 × 10-48 esu and electro-optic coefficients r33 reaching 650 pm V-1. One highlight is that the electro-optic films of the β-branched chromophores are superior in terms of thermal stability in device operation as measured by a transmissive modified reflective Teng-Man method. This work provides guidelines for the design of improved electro-optic materials including β-branched chromophores which could be useful for practical EO applications, where both enhanced β and r33 values together with chemical and thermal stability are necessary.

Carbon nanohorns have been functionalized with oligothiophene units via the 1,3-dipolar cycloaddition reaction under microwave irradiation and solvent-free conditions. A dramatic Raman enhancement was found for one of the synthesized derivatives. Experimental and in silico studies helped to understand the enhancement, attributed to the modification of electromagnetic fields upon functionalization at the tip of the nanostructures.

Insulated polythiophenes with a polyrotaxane-like 3D architecture have shown excellent intrawire hole mobility, allowing their use in interesting optoelectronic applications. This is due to the isolation of the π-conjugated backbones that warrants for stabilization of the quasi-planar conformation of the polythiophene core and prevents electronic communication between adjacent chains. Thus, polythiophene-based insulated molecular wires (IMWs) constitute ideal test-beds to evaluate the structural changes within the conjugated polymer chain, such as intrachain conformation and π-electron delocalization. Here, we investigate the structure and spectroscopic response of fully and partially insulated polythiophene-based IMWs. An experimental investigation of Raman spectra supported by density functional theory (DFT) calculations allows us to give a detailed interpretation of intramolecular interactions, highlighting differences in π-electron conjugation revealed by the presence of an intensity transfer between the two main Raman modes associated with the C═C/C–C stretching vibrations. This study proves the sensitivity of Raman spectroscopy as a technique to monitor structural changes in self-encapsulated conjugated polymers. This work at the University of Málaga was funded by the MICINN (PID2019-110305GB-I00) and Junta de Andalucía (UMA18-FEDERJA-080, P09FQM-4708, and P18-FR-4559) projects. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the SCBI (Supercomputing and Bioinformatics) Center of the University of Malaga. Funding for open access charge: Universidad de Málaga / CBUA.

Four highly porous truxene-based organic polymers have been synthesized via C–C cross coupling methodologies (under Yamamoto and Suzuki–Miyaura conditions) starting from two different brominated he...

A series of donor-acceptor-acceptor (D-A-A) and donor-acceptor-donor (D-A-D) systems based on a pyrimidine π-spacer with various substituents at the C-2 position has been successfully prepared. The synthesis involved site-selective palladium cross-coupling reactions of chloropyrimidines with triorganoindium reagents and proceed in good yields and with atom economy. 4-(

Monomers 4,7-dibromo-2H-benzo[d]1,2,3-triazole (m1) and 4,7-(bis(4-bromophenyl)ethynyl)-2H-benzo[d]1,2,3-triazole (m2) have been synthesized in good yields using different procedures. Monomers m1 and m2 have been employed for building new copolymers of fluorene derivatives by a Suzuki reaction under microwave irradiation using the same conditions. In each case different chain lengths have been achieved, while m1 gives rise to polymers for m2 oligomers have been obtained (with a number of monomer units lower than 7). Special interest has been paid to their photophysical properties due to excited state properties of these D-A units alternates, which have been investigated by density functional theory (DFT) calculations using two methods: (i) An oligomer approach and (ii) by periodic boundary conditions (PBC). It is highly remarkable the tunability of the photophysical properties as a function of the different monomer functionalization derived from 2H-benzo[d]1,2,3-triazole units. In fact, a strong modulation of the absorption and emission properties have been found by functionalizing the nitrogen N-2 of the benzotriazole units or by elongation of the &pi, conjugated core with the introduction of alkynylphenyl groups. Furthermore, the charge transport properties of these newly synthesized macromolecules have been approached by their implementation in organic field-effect transistors (OFETs) in order to assess their potential as active materials in organic optoelectronics.

A new design paradigm for the production of low band gap polymers is reported, in which an ambipolar unit exhibiting both donor and acceptor properties is combined with a conventional acceptor. As ...

International audience; Introducing one or two alkynyl-iron moieties onto a carbo[6]helicene results in organometallic helicenes (2 a,b) that display strong chiroptical activity combined with efficient redox-triggered switching. The neutral and oxidized forms have been studied in detail by electronic and vibrational circular dichroism, as well as by Raman optical activity (ROA) spectroscopy. The experimental results were analyzed and spectra were assigned with the help of first-principles calculations. In particular, a recently developed method for ROA calculations under resonance conditions has been used to study the intricate resonance effects on the ROA spectrum of mono-iron ethynylhelicene 2 a.

In the present paper, the synthesis and characterization of 2,2′-bis{bi[2,2’-(3,4-ethylenedioxy)thiophen-5-yl]}-3,3′-bithianaphthene, nicknamed BT2E4, is reported. We show that electrooligomerization of BT2E4 leads to electroactive films which are evaluated by cyclic voltammetry (CV), UV/vis spectroelectrochemistry and CV coupled with in-situ conductance measurements. Direct comparisons to the properties of the oligomers obtained from the atropisomeric all-thiophene analogue BT2T4 show that the introduction of EDOT leads to a strong reduction of the band-gap, an overall red-shifted absorption spectrum and a rigidification of the structure. Finally, DFT and TD-DFT calculations were performed in parallel to investigate and to compare the electronic and molecular structures of neutral and charged monomer and oligomer species.

The electronic and photophysical properties of a disk-like molecule that combines two electron donor and one electron acceptor segments in a π-conjugated planar backbone, namely, 10-dihydro-15H-indeno[1,2-a]indolo[3,2-c]carbazol-15-one (diazatruxenone) have been investigated through a joint experimental and theoretical study, in order to explore its potential applications in the area of organic electronics. The influence that peripheral substitution and functionalization at the bridging nitrogens exerts on the electronic properties as well as in the supramolecular arrangement of this donor–acceptor scaffold has also been investigated. It has been found that by varying the electronic nature of the attached peripheral groups it is possible to tune its redox and optical properties. On the other hand, N-alkylation barely affects its electronic properties; however, it strongly influences how molecules interact with each other in the bulk. Interestingly, the calculated charge-transport parameters (reorganization energy and electronic coupling) confirm the potential of this disk-shaped platform to act as an ambipolar charge transporter.

In this paper, experimental and computational investigations are combined to analyze the impact of the diradical character in the photonic and chemical properties of two tetracyano quinodimethane derivatives of phenylene-vinylenes. The photonic properties are evaluated with high-level quantum-chemical calculations and are rationalized in the context of the four-level model typical of diradical molecules, including one triplet and three singlet states, whereas the diradical extent in the ground electronic state is shown to be the driving force for the dimerization reactions. To this end DFT, CASSCF, and CASPT2//CASSCF calculations are carried out and complemented with experimental UV-vis-NIR absorption and emission measurements, as a function of the temperature along with resonance Raman spectroscopy investigations. The study of diradical molecules with enhanced chemical stability in the framework of organic electronics is an important field of research in organic π-conjugated molecules with direct applications in organic electronics.

A series of novel imide-functionalized ladder-type heteroarenes with well-defined structure and controllable conjugation lengths were synthesized and characterized. The synthetic route shows remarkable efficacy for constructing the electron-deficient ladder backbones. π-Conjugation extension leads to narrowed band gaps with enhanced electron affinities. The ladder arenes are incorporated into organic thin-film transistors, and show encouraging electron mobilities of 0.013–0.045 cm2 V−1 s−1. The heteroarenes reported here provide a remarkable platform for fundamental physicochemical studies and materials innovation in organic electronics.

Carbon-bridged bis(aminoaryl) oligo(para-phenylenevinylene)s have been prepared and their optical, electrochemical, and structural properties analyzed. Their radical cations are class III and class II mixed-valence systems, depending on the molecular size, and they show electronic couplings which are among the largest for the self-exchange reaction of purely organic molecules. In their dication states, the antiferromagnetic coupling is progressively tuned with size from quinoidal closed-shell to open-shell biradicals. The data prove that the electronic coupling in the radical cations and the singlet–triplet gap in the dications show similar small attenuation factors, thus allowing charge/spin transfer over rather large distances. ·, We thank MINECO of the Spanish Government (CTQ2015- 69391-P, CTQ2013-40480-R and MAT2015-66856-R) for their support. We also thank the Research Central Services (SCAI) of the University of M#laga. This work is partially supported by Grant-in-Aid for Scientific Research (16H04106 to HTand 15H05754 to EN) and the Strategic Promotion of Innovative Research, JST (to EN) from MEXT, Japan. M.H. and C.L. are grateful to the Deutsche Forschungsgemeinschaft for supporting this work (GRK 2112).

Conducting polymers can be synthesized by irreversible diradical monomer polymerization. A reversible version of this reaction consisting of the formation/dissociation of σ‐dimers and σ‐polymers from a stable quinonoidal diradical precursor is described. The reaction reversibility is made by a quinonoidal molecule which changes its structure to an aromatic species by forming weak and long intermolecular C−C single bonds. The reaction provokes a giant chromic effect of about 2.5 eV. The two opposite but complementary quinonoidal and aromatic tautomers provide the Janus faces of the reactants and products which produces the observed chromic effect. A reaction mechanism is proposed to explain the variety of final products starting with structurally very similar reactants. These reversible reactions, covering an unusual regime of weak covalent supramolecular bonding, yield products which might be envisaged as novel molecular and polymeric soft matter phases.

Three new hexaazatriphenylene (HAT)-based electron-accepting molecules with octupolar disc-like symmetry that combine the HAT core with six branches of electron-donor thiophenes in two modalities have been synthesized: (i) with six donor thiophenes and bithiophenes delineating a six-donor-to-one-acceptor (6–1) profile and (ii) with six donor–acceptor branches configuring a 6–6–1 acceptor–donor–acceptor triad. The 6-fold accumulation of donors and acceptors in the periphery of the HAT core is expected to tune the molecular electronic and optical properties. An exhaustive analysis of these properties as a function of the 6–1 and 6–6–1 stoichiometry of the molecules is described by combining a palette of experimental spectroscopic techniques such as electronic absorption (from the ground electronic and excited states), emission (fluorescence and phosphorescence), ultraviolet photoelectron spectroscopy, spectroelectrochemistry, and vibrational Raman have been implemented, all combined with electrochemistry an...

Radical cations and dications of [n]CPP from n = 5 to n = 12 have been studied by Raman spectroscopy and density functional theory. Small [n]CPP dications owe their stability to the closed-shell electronic structure imposed by cyclic conjugation surpassing the destabilizing effect of ring strain and of the electron deficiency of the charged states. Large [n]CPP dications mitigate cyclic strain by forming diradicals. The Raman spectra reflect the balance among cyclic conjugation, cyclic strain and biradicaloid stabilization by finding an unexpected turning point in the frequency behavior of the G vibrational modes as a function of size. These Raman data represent the vibrational fingerprint of this rare form of conjugation which is central to stabilize both cations and dications of [n]CPP macrocycles.

Open-shell singlet diradicaloids have recently received much attention due to their unique optical, electronic and magnetic properties and promising applications in materials science. Among various diradicaloids, quinoidal π-conjugated molecules have become the prevailing design. However, the need for a fundamental understanding on how the fusion mode and pro-aromaticity/anti-aromaticity affect their diradical character and physical properties remains unaddressed. In this work, a series of pro-aromatic benzo-thia-fused [n]thienoacenequinodimethanes (Thn-TIPS (n = 1-3) and BDTh-TIPS) were synthesized and compared with the previously reported anti-aromatic bisindeno-[n]thienoacenes (Sn-TIPS, n = 1-4). The ground-state geometric and electronic structures of these new quinoidal molecules were systematically investigated by X-ray crystallographic analysis, variable temperature NMR, ESR, SQUID, Raman, and electronic absorption spectroscopy, assisted by DFT calculations. It was found that the diradical character index (y0) increased from nearly zero for Th1-TIPS to 2.4% for Th2-TIPS, 18.2% for Th3-TIPS, and 38.2% for BDTh-TIPS, due to the enhanced aromatic stabilization. Consequently, with the extension of molecular size, the one-photon absorption spectra are gradually red-shifted, the two-photon absorption (TPA) cross section values increase, and the singlet excited state lifetimes decrease. By comparison with the corresponding anti-aromatic analogues Sn-TIPS (n = 1-3), the pro-aromatic Thn-TIPS (n = 1-3) exhibit larger diradical character, longer singlet excited state lifetime and larger TPA cross section value. At the same time, they display distinctively different electronic absorption spectra and improved electrochemical amphotericity. Spectroelectrochemical studies revealed a good linear relationship between the optical energy gaps and the molecular length in the neutral, radical cationic and dicationic forms. Our research work discloses a significant difference between the pro-aromatic and anti-aromatic quinoidal compounds and provides guidance for the design of new diradicaloids with desirable properties.

Cyclic paraphenylenes, [n]CPPs, and linear paraphenylenes, [n]LPPs, formed by n benzenes, are investigated by Raman spectroscopy for n = 5 to 12 and density functional theory (DFT) for n = 4 to 20. The information on the experimental Raman frequencies and intensities, combined with DFT computations and reported X-ray diffraction structures, provides a consistent interpretation of the Raman spectra and allows establishing relevant structure-property trends. Structural and electronic effects such as benzene ring bending, inter-ring torsions, π-conjugation (aromaticity) and orbital energy gaps as a function of the linear elongation in [n]LPPs versus the macrocyclic curvature in [n]CPPs and of the molecular size (i.e., polymer limit) are systematically analyzed on the basis of the vibrational Raman properties. Changes in the BLA as an indicator of the degree of quinonoid character are analyzed and linked to the Effective Conjugation Coordinate (ECC) model. The BLA patterns involved in twisted and non-twisted conformations and in different species (bipolarons, quinonoid tautomers, and ECC active modes) are compared and their differences are discussed. This paper offers a unified interpretation of structural and electronic aspects in relation to the evolution from linear 1D π-systems to cyclic 2D structures.

Chromophores where a polyenic spacer separates a 4H-pyranylidene or benzothiazolylidene donor and three different butenolide nitriles have been synthesized and characterized. The role of 2(5H)-furanones as acceptor units on the polarization and the second-order nonlinear (NLO) properties has been studied. Thus, their incorporation gives rise to moderately polarized structures with NLO responses that compare favorably to those of related compounds featuring more efficient electron-withdrawing moieties. Derivatives of the proaromatic butenolide PhFu show the best nonlinearities. Benzothiazolylidene-containing chromophores present less alternated structures than their pyranylidene analogues, and, unlike most merocyanines, the degree of charge transfer does not decrease on lengthening the π-bridge., Financial support from MICINN-FEDER (CTQ2011-22727 and MAT2011-27978- C02-02), MINECO (CTQ2014-52331R), and Gobierno de Aragon-Fondo Social Europeo (E39 and E04) is gratefully acknowledged. Research at the Universidad de Malaga was supported by MINECO (CTQ2012-33733) and Junta de Andalucıa (P09-4708).

Development of high-performance unipolar n-type organic semiconductors still remains as a great challenge. In this work, all-acceptor bithiophene imide-based ladder-type small molecules BTIn and semiladder-type homopolymers PBTIn (n = 1–5) were synthesized, and their structure–property correlations were studied in depth. It was found that Pd-catalyzed Stille coupling is superior to Ni-mediated Yamamoto coupling to produce polymers with higher molecular weight and improved polymer quality, thus leading to greatly increased electron mobility (μe). Due to their all-acceptor backbone, these polymers all exhibit unipolar n-type transport in organic thin-film transistors, accompanied by low off-currents (10–10–10–9 A), large on/off current ratios (106), and small threshold voltages (∼15–25 V). The highest μe, up to 3.71 cm2 V–1 s–1, is attained from PBTI1 with the shortest monomer unit. As the monomer size is extended, the μe drops by 2 orders to 0.014 cm2 V–1 s–1 for PBTI5. This monotonic decrease of μe was al...

A detailed analysis is undertaken of positively charged species generated on a series of thienylenevinylene (nTV) wires terminally substituted with two perchlorotriphenylmethyl (.PTM) radical acceptor groups, .PTM‐nTV‐PTM. (n=2–7). Motivated by the counterintuitive key role played by holes in the nTV bridges on the operating mechanism of electron transfer in their radical anion mixed‐valence derivatives, a wide combination of experimental and theoretical techniques is used, with the aim of gaining further insights into their structural location. Consequently, contributions of the .PTM units for the stabilization of the radical cations and hole localization, particularly in the case of the shortest molecular wire, are probed. In this sense, the formation of quinoidal ring segments, resulting from the coupling of the unpaired electron of the .PTM radical site with those generated along the nTV chains is found. Additionally, open‐shell dications, described by the recovery of the central aromaticity and two terminal quinoidal segments, assisted by the .PTM units, are detected., The authors acknowledge the financial support through pro-jects: BE-WELL (CTQ2013-40480-R), FANCY (CTQ2016-80030-R), CTQ2015- 69391-P and CTQ2016-79189-R, grant-ed by the DGI (Spain), GenCat (2014-SGR-17) financed by DGR (Catalunya) and the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496) and project PEII-2014-014-P granted by the Junta de Comunidades de Castilla-La Mancha, Spain. This study has been also supported by the Networking Research Center on Bioengineering, Bio-materials and Nanomedicine (CIBER-BBN), an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and fi-nanced by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. The authors also thank the Research Central Services (SCAI) of the Uni-versity of Málaga. P. M. B. gratefully acknowledges financial support from the Juan de la Cierva-Formación 2015 pro-gramme supported by MINECO. We also acknowledge Dr. Vega Lloveras for the EPR measurements.

The synthesis, self-assembly, and semiconducting properties of a series of disk-like truxenone derivatives, functionalized with three peripheral long alkyl chains, either directly attached or distanced by linking phenyl or ethynyl groups, are reported. The strategy of distancing the alkyl chains from the central aromatic cores induces in these discotics well-ordered columnar assemblies and has a favorable effect on their charge-carrier mobility. Electron mobility values above 1 cm2 V-1 S-1 were determined for a truxenone functionalized with three peripheral decynyl chains by means of the space charge-limited current technique. DFT calculations help to rationalize the high mobility values found for these new truxenone-based systems, indicating efficient intermolecular electronic couplings (fostered by a favorable stacking configuration) and moderate intramolecular reorganization energies for electrons in the origin of such high mobilities.

As effective building blocks for high-mobility transistor polymers, oligothiophenes are receiving attention for polymer solar cells (PSCs) because the resulting polymers can effectively suppress charge recombination. Here we investigate two series of in-chain donor-acceptor copolymers, PTPDnT and PBTInT, based on thieno[3,4-c]pyrrole-4,6-dione (TPD) or bithiopheneimide (BTI) as electron acceptor units, respectively, and oligothiophenes (nTs) as donor counits, for high-performance PSCs. Intramolecular S···O interaction leads to more planar TPD polymer backbones, however backbone torsion yields greater open-circuit voltages for BTI polymers. Thiophene addition progressively raises polymer HOMOs but marginally affects their band gaps. FT-Raman spectra indicate that PTPDnT and PBTInT conjugation lengths scale with nT catenation up to n = 3 and then saturate for longer oligomer. Furthermore, the effects of oligothiophene alkylation position are explored, revealing that the alkylation pattern greatly affects film morphology and PSC performance. The 3T with "outward" alkylation in PTPD3T and PBTI3T affords optimal π-conjugation, close stacking, long-range order, and high hole mobilities (0.1 cm(2)/(V s)). These characteristics contribute to the exceptional ∼80% fill factors for PTPD3T-based PSCs with PCE = 7.7%. The results demonstrate that 3T is the optimal donor unit among nTs (n = 1-4) for photovoltaic polymers. Grazing incidence wide-angle X-ray scattering, transmission electron microscopy, and time-resolved microwave conductivity measurements reveal that the terthiophene-based PTPD3T blend maintains high crystallinity with appreciable local mobility and long charge carrier lifetime. These results provide fundamental materials structure-device performance correlations and suggest guidelines for designing oligothiophene-based polymers with optimal thiophene catenation and appropriate alkylation pattern to maximize PSC performance.

Research on stable open-shell singlet diradicaloids recently became a hot topic because of their unique optical, electronic, and magnetic properties and promising applications in materials science. So far, most reported singlet diradicaloid molecules have a symmetric structure, while asymmetric diradicaloids with an additional contribution of a dipolar zwitterionic form to the ground state were rarely studied. In this Article, a series of new push-pull type oligo(N-annulated perylene)quinodimethanes were synthesized. Their chain length and solvent-dependent ground states and physical properties were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, Raman spectroscopy, and electrochemistry. It was found that with extension of the chain length, the diradical character increases while the contribution of the zwitterionic form to the ground state becomes smaller. Because of the intramolecular charge transfer character, the physical properties of this push-pull system showed solvent dependence. In addition, density functional theory calculations on the diradical character and Hirshfeld charge were conducted to understand the chain length and solvent dependence of both symmetric and asymmetric systems. Our studies provided a comprehensive understanding on the fundamental structure- and environment-property relationships in the new asymmetric diradicaloid systems.

New dimers with two triindole subunits bound together through different linkers (p-phenylene or diacetylene groups) have been synthesized and studied as model systems to determine the differences in the electron transfer ability of the two bridging units. Our results show that whereas a p-phenylene bridge nearly isolates the two subunits of the dimers a diacetylene bridge allows a high level of electronic connection between them., This work was financially supported by the MINECO of Spain (CTQ2012-33733 and CTQ2013-40562-R) and the Comunidad de Madrid S2013/MIT-2740 and Junta de Andalucía (P09-FQM-4708). M.C.R.D. thanks the MICINN for a “Ramón y Cajal” Research contract. S2013/MIT-2740-PHAMA_2.0

We report the process of singlet exciton fission with high-yield upon photoexcitation of a quinoidal thiophene molecule. Efficient ultrafast triplet photogeneration and its yield are determined by photoinduced triplet-triplet absorption, flash photolysis triplet lifetime measurements, as well as by femtosecond time-resolved transient absorption and fluorescence methods. These experiments show that optically excited quinoidal bithiophene molecule undergoes ultrafast formation of the triplet-like state with the lifetime ∼57 μs. CASPT2 and RAS-SF calculations have been performed to support the experimental findings. To date, high singlet fission rates have been reported for crystalline and polycrystalline materials, whereas for covalently linked dimers and small oligomers it was found to be relatively small. In this contribution, we show an unprecedented quantum yield of intramolecular singlet exciton fission of ∼180% for a quinoidal bithiophene system.

We have used Raman spectroscopy to study the molecular and electronic structures of the radical cations and dications of carbon-bridged oligo(para-phenylenevinylene)s (COPVn, n = 1-6) possessing consecutive fused pentagons and hexagons, up to 19, along with COPV derivatives having electron-donating and -withdrawing groups. This study was made possible by the outstanding stability of the charged states of COPVs. We could untangle the effects of π-conjugation in the planar structure on the Raman frequency by distinguishing it from other structural effects, such as strain in the vinylene groups shared by the two pentagons. The analyses showed that the radical cations have benzo-quinoidal structures confined in the center of the molecule, as well as benzo-aromatic rings at the terminal sites. In contrast, dications of COPVn longer than n = 3 exhibit a biradicaloid character because of the recovery of aromaticity in the central rings and quinoidal rings at the terminal positions. These biradicaloids favor a singlet nature in their ground electronic states because of the double spin polarization. The introduction of electron-donating and -withdrawing groups on the termini of a COPV core affords, upon oxidation or reduction, a fully delocalized class III mixed valence system because of the high degree of conjugation of the COPV platform, which favors extensive charge delocalization.

Aromaticity is an important concept to understand the stability and physical properties of π-conjugated molecules. Recent studies on pro-aromatic and anti-aromatic molecules revealed their irresistible tendency to become diradicals in the ground state. Diradical character thus becomes another very important concept and it is fundamentally correlated to the physical (optical, electronic and magnetic) properties and chemical reactivity of most of the organic optoelectronic materials. Molecules with distinctive diradical character show unique properties which are very different from those of traditional closed-shell π-conjugated systems, and thus they have many potential applications in organic electronics, spintronics, non-linear optics and energy storage. This critical review first introduces the fundamental electronic structure of Kekulé diradicals within the concepts of anti-aromaticity and pro-aromaticity in the context of Hückel aromaticity and diradical character. Then recent research studies on various stable/persistent diradicaloids based on pro-aromatic and anti-aromatic compounds are summarized and discussed with regard to their synthetic chemistry, physical properties, structure-property relationships and potential material applications. A summary and personal perspective is given at the end.

We have performed a multiscale approach to study the influence of peripheral substitution in the semiconducting properties of discotic liquid-crystalline triindoles. Charge carrier mobility as high as 1.4 cm V s was experimentally reported for triindoles substituted with alkynyl chains on the periphery (Gómez-Lor et al. Angew. Chem., Int. Ed., 2011, 50, 7399-7402). In this work, our goal is to get a deeper understanding of both the molecular electronic structure and microscopic factors affecting the charge transport properties in triindoles as a function of the spacer group connecting the central cores with the external alkyl chains (i.e., alkyne or phenyl spacers groups). To this end, we first perform Quantum Mechanical (QM) calculations to assess how the peripheral substitution affects the electronic structure and the internal reorganization energy. Secondly, boxes of stacked molecules were built and relaxed through molecular dynamics to obtain realistic structures. Conformational analysis and calculations of transfer integrals for closed neighbours were performed. Our results show that the insertion of ethynyl spacers between the central aromatic core and the flexible peripheral chains results in lower reorganization energies and enhanced intermolecular order within the stacks with a preferred cofacial 60° staggered conformation, which would result in high charge-carrier mobilities in good agreement with the experimental data. This work allows a deeper understanding of charge carrier mobility in columnar phases, linking the structural order at the molecular level to the property of interest, i.e. the charge carrier mobility. We hope that this understanding will improve the design of systems at the supramolecular level aiming at obtaining a more defined conducting channel, higher mobility and smaller fluctuations within the column., D.A.S.F. gratefully acknowledges the financial support from CNPq, grants 304020/2016-8 and 407682/2013-9, and FAP-DF grants 0193.001.062/2015 and 193.001.284/2016. ML thanks SeRC (Swedish e-Science Research Center) for funding and SNIC (Swedish National Infrastructure for Computing) for providing computer resources (project ID snic2015-1-420). Research at University of Malaga was supported by MINECO (CTQ2015-66897-P) and Junta de Andalucia (P09-4708). BGL acknowledges the financial support from MINECO (CTQ2016-78557-R) and Comunidad de Madrid S2013/MIT.

New stilbenoid and thiophenic compounds terminally functionalized with donor-donor, acceptor-acceptor, or donor-acceptor moieties and possessing a central [2.2]paracyclophane unit have been prepared, and their properties interpreted in terms of through-bond and through space π-electron delocalization (i.e., π-conjugations). Based on photophysical data, their excited-state properties have been described with a focus on the participation of the central [2.2]paracyclophane in competition with through-bond conjugation in the side arms. To this end, two-photon and one-photon absorption and emission spectroscopy, as a function of temperature, solvent polarity, and pressure in the solid state have been recorded. Furthermore, charge delocalization through the [2.2]paracyclophane in the neutral state and in the oxidized species (radical cations, dications and radical trications) has been investigated, allowing the elucidation of the vibrational Raman fingerprint of through-space charge delocalization. Thus, a complementary approach to both "intermolecular" excitation and charge delocalizations in [2.2]paracyclophane molecules is shown which can serve as models of charge and exciton migration in organic semiconductors.

Franco, Carlos et al., Charge transfer/transport in molecular wires over varying distances is a subject of great interest The feasible transport mechanisms have been generally accounted for on the basis of tunneling or superexchange charge transfer operating over small distances which progressively gives way to hopping transport over larger distances. The underlying molecular sequential steps that likely take place during hopping and the operative mechanism occurring at intermediate distances have received much less attention given the difficulty in assessing detailed molecular-level information. We describe here the operating mechanisms for unimolecular electron transfer/transport in the ground state of radical-anion mixed-valence derivatives occurring between their terminal perchlorotriphenylmethyl/ide groups through thiophene-vinylene oligomers that act as conjugated wires of increasing length up to 53 Å. The unique finding here is that the net transport of the electron in the larger molecular wires is initiated by an electron-hole dissociation intermediated by hole delocalization (conformationally assisted and thermally dependent) forming tran-sient mobile polaronic states in the bridge that terminate by an electron-hole recombination at the other wire extreme. On the con-trary for the shorter radical-anions our results suggest that a flickering resonance mechanism which is intermediate between hop-ping and superexchange is the operative one. We support these mechanistic interpretations by applying the pertinent biased kinetic models of the charge/spin exchange rates determined by electron paramagnetic resonance and by molecular structural level infor-mation obtained from UV-Vis and Raman spectroscopies and by quantum chemical modelling., We acknowledge the financial support from the Spanish MINECO/FEDER (grants CTQ2013-40480-R, CTQ2016- 7989-R, and CTQ2015-64618-R), Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (grant SEV2015-0496), the Generalitat de Catalunya (grants 2014SGR-17, 2014SGR-97, and XRQTC). We also acknowledge supercomputing resources provided by the Red Españ ola de Supercomputacion and the Networking Research Center of Bioengineering, Biomaterials and Nanomedicine (CIBERBBN). The work carried out at the University of Malaga was supported by MINECO/FEDER through the reference projects CTQ2012-33733 andCTQ2015-69391-P. The “Servicios Centrales de Apoyo a la Investigacioń ” of the University of Malaga are also acknowledged by generous access to its facilities. I.A. acknowledges the Spanish Ministerio de Educacion Cultura y Deporte for a FPU PhD scholarship.

Quinoidal-vs.-aromatic synergy: Cyclopentadithiophene-vinylene oligomers with different sizes, in different oxidation states and as pro-aromatic quinoidals are studied considering balanced contributions of aromatic and quinoidal forms., A new series of π-conjugated oligomers based on the 4,4 dihexyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene vinylene repeating unit has been prepared and characterized by X-ray, electrochemical, spectroscopic (UV-Vis absorption, emission and Raman) and density functional theory methods. The oligomers in their neutral, oxidized and reduced forms have been investigated. The neutral compounds show a longer mean conjugation length than oligothiophenes and oligothiophene-vinylenes and display very rich redox chemistry with the stabilization of polycationic states of which the radical cations and dications are strong NIR absorbers, the latter displaying singlet diradicaloid character. An interesting complementarity between the sequence of aromatic-quinoidal structural segments in the radical cations and dications has been described and interpreted. Two derivatives with the 4,4 dihexyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene vinylene unit, disubstituted either with electron donor, bis(triaryl amino) groups, or acceptors bis(dicyano-methylene) caps enforcing a quinoidal structure in the dithiophene-vinylene bridge, have been also synthesized and characterized. The radical cation of the triarylamine compound and the radical anion of the tetracyano compound similarly display hole and electron charge localization, or confinement, in the nitrogen and dicyano surrounding parts, or class II mixed valence systems, while their dication and dianion species, conversely, are open-shell diradical (i.e., polaron pair) and closed-shell (i.e., bipolaron), respectively. The preparation of these new π-conjugated oligomers gives way to the realization of compounds with new electronic properties and unique structures potentially exploitable in organic electronics.

Oligomers of ethylendioxythiophene-vinylene have been prepared. Their optical, electrochemical and chemical properties have been studied in detail by absorp- tion and emission spectroscopy as well as cyclic voltamme- try, Raman techniques and spectroelectrochemistry comple- mented with quantum chemical calculations. A comparison with their non-ethylendioxy and non-vinylene parents has been done. The inclusion of the EDO plus the vinylene func- tion generates more robust electronic ground states regard- ing the largely flexible thiophene-vinylene (n TV) oligomeric homologues. The redox features of the new compounds are also rich of oxidative processes arising as an interesting sta- bilising balance effect between the oxygen fragment in the EDO groups (mesomeric effect) and the linear p-conjugated structure. The oxidised species have been characterised, which show the ability for the formation of mixed valence charge-transfer complexes and p dimers of different oxida- tion states, in particular, in the electrochemical medium, re- sulting that the electrochemical response is accounted for a succession of aggregation and electron-transfer steps. With this work, a full understanding of the optical and elec- tronic properties of these new oligomers in the context of the oligomer approach has been proposed.

The controlled synthesis of branched polythiophenes via Ni-catalyzed Kumada type coupling of branched AB2 monomers prepared in situ from 5,5′′-dibromo-2,2′:3′,2′′-terthiophene (3TBr2) and 5,5′,5′′-tribromo-2,2′:3′,2′′-terthiophene (3TBr3) is presented. The access to highly branched polymer architectures with rather high molecular weights is a key benefit of this one-pot polymerization with respect to standard oxidative polymerization procedures. Our synthetic route further allows the in situ endgroup functionalization as shown exemplarily for pentene functionalized branched polythiophenes and eases thereby the access to branched polythiophenes with tailor-made properties. In particular a comparison of the optical properties allows conclusions about the architecture of the obtained materials with respect to linear and fully branched systems. Energy levels are obtained by cyclic voltammetry measurements in thin films. DFT calculations provide further guidance on the interpretation of the possible molecular structure of the polymer (i.e. branching density) in correlation with their properties.

Radical cations of a heptathienoacene α,β-substituted with four n-decyl side groups (D4T7(.) (+) ) form exceptionally stable π-dimer dications already at ambient temperature (Chem. Comm. 2011, 47, 12622). This extraordinary π-dimerization process is investigated here with a focus on the ultimate [D4T7(.) (+) ]2 π-dimer dication and yet-unreported transitory species formed during and after the oxidation. To this end, we use a joint experimental and theoretical approach that combines cyclic voltammetry, in situ spectrochemistry and spectroelectrochemistry, EPR spectroscopy, and DFT calculations. The impact of temperature, thienoacene concentration, and the nature and concentration of counteranions on the π-dimerization process is also investigated in detail. Two different transitory species were detected in the course of the one-electron oxidation: 1) a different transient conformation of the ultimate [D4T7(.) (+) ]2 π-dimer dications, the stability of which is strongly affected by the applied experimental conditions, and 2) intermediate [D4T7]2 (.) (+) π-dimer radical cations formed prior to the fully oxidized [D4T7]2 (.) (+) π-dimer dications. Thus, this comprehensive work demonstrates the formation of peculiar supramolecular species of heptathienoacene radical cations, the stability, nature, and structure of which have been successfully analyzed. We therefore believe that this study leads to a deeper fundamental understanding of the mechanism of dimer formation between conjugated aromatic systems.

[n]Cycloparaphenylenes behave as molecular templates of "perfectly chemically defined" single-wall carbon nanotubes. These [n]CPP molecules have electronic, mechanical, and chemical properties in size correspondence with their giant congeners. Under mechanical stress, they form charge-transfer salts, or complexes with fullerene, by one-electron concave-convex electron transfer.

Here we present the synthesis and optical and structural characterization of a new series of alternating donor–acceptor copolymers based on 3,4-ethylenedioxythiophene (EDOT). The donor consists of phenylene, alkylated fluorene, or diethynyl-1,4-phenylene as the aryl units copolymerized with the EDOT group with and without a 9,10-anthraquinone (AQ) side chain as the acceptor group, namely, as PEX-AQ and PEX, respectively. The changes in the electronic absorption/emission spectra and redox properties are analyzed in detail as a function of (i) the composition of the copolymers and (ii) the inclusion of the pendant 9,10-anthraquinone. Density functional theory calculations are used to interpret the experimental results. Special emphasis is placed on the flexibility of the phenylene-based copolymer spine which favors the tendency toward aggregation and confers interesting solvathocromic, thermochromic, and sonochromic properties when applying external stimuli. This is explained by means of an order–disorder c...

Herein we present novel Raman spectroscopic studies carried out for polyselenophene (PSe), poly(3,4-ethylenedioxyselenophene) (PEDOS), and alkyl-substituted poly(alkyl-3,4-ethylenedioxyselenophene) (PEDOS-Cn: n=2, 8, and 12) homologues. These spectroscopic data are combined with morphological and structural analysis techniques, such as AFM, and DFT simulations. An investigation into the extent of π-conjugation in PSe is presented by comparing its spectral signatures with those of a homologous series of oligoselenophenes. Our experimental data suggest that π-conjugation in the PSe backbone extends to more than six selenophene units. The incorporation of ethylenedioxy (EDO) groups in PEDOS results in a more complex spectrum and a downshift of the CC/CC stretching vibration (or effective conjugation coordinate (ECC) mode); this provides evidence for an improvement in the π-conjugational properties along the PSe backbone upon EDO substitution. The dispersity of π-conjugation lengths in different PEDOS samples obtained through different synthetic routes is evaluated as a function of different structural factors. Finally, we present experimental evidence that the insertion of alkyl chains into the EDO units slightly impacts on the π-conjugational properties of the PEDOS backbone in the non-annealed samples (with an improved π-electron delocalization found in PEDOS-C8), but moderately affects the degree of molecular order of polymer films upon thermal annealing.

The electronic and photophysical properties of 6,11-dihydro-5H-diindolo[2, 3-a:2′,3′-c]carbazole, an asymmetric cyclic dehydrotrimer of indole, have been explored and compared to its symmetric analogue, 10,15-dihydro-5H- diindolo[3,2-a:3′,2′-c]carbazole (triindole), a well-known high hole mobility semiconductor. To this purpose, we use a joint experimental and theoretical approach that combines absorption and emission spectroscopies, cyclic voltammetry, and spectroelectrochemistry with DFT calculations. Lowering the symmetry of the triindole platform causes a red-shift of the absorption edge and emission maxima and improved the fluorescence quantum yield. Cyclic voltammetry and spectroelectrochemistry reveal the reversible nature of the two observable oxidation processes in the alkylated asymmetric triindoles together with an increase in the stabillity of their oxidized species. On the other hand, the insertion of alkyl groups on the nitrogen atoms results in a further fluorescence enhancement although larger reorganization energies are found. DFT and time-dependent (TD-DFT) calculations successfully support the experimental data and aid in the understanding of the tuning of the physicochemical properties of the triindole platform upon symmetry lowering toward their incorporation in electronic devices. © 2014 American Chemical Society., This work was financially supported by the MICINN of Spain (CTQ2010-18813) and the CAM (Project S2009/MAT-1756/CAM), MINECO of Spain (CTQ2012-33733), Junta de Andalucía (P09-FQM-4708). M.C.R.D. thanks the MICINN for a “Ramón y Cajal” Research contract. D.A.S.F. gratefully acknowledges the financial support from the Brazilian Research Councils CNPq CAPES, CNPq (grant 303084/2010-3) and FAP-DF (Fundaçâo de Apoio à Pesquisa do Distrito Federal).

Recent studies demonstrated that aromaticity and biradical character play important roles in determining the ground-state structures and physical properties of quinoidal polycyclic hydrocarbons and oligothiophenes, a kind of molecular materials showing promising applications for organic electronics, photonics and spintronics. In this work, we designed and synthesized a new type of hybrid system, the so-called bisindeno-[n]thienoacenes (n = 1–4), by annulation of quinoidal fused α-oligothiophenes with two indene units. The obtained molecules can be regarded as antiaromatic systems containing 4n π electrons with small singlet biradical character (y0). Their ground-state geometry and electronic structures were studied by X-ray crystallographic analysis, NMR, ESR and Raman spectroscopy, assisted by density functional theory calculations. With extension of the chain length, the molecules showed a gradual increase of the singlet biradical character accompanied by decreased antiaromaticity, finally leading to a highly reactive bisindeno[4]thienoacene (S4-TIPS) which has a singlet biradical ground state (y0 = 0.202). Their optical and electronic properties in the neutral and charged states were systematically investigated by one-photon absorption, two-photon absorption, transient absorption spectroscopy, cyclic voltammetry and spectroelectrochemistry, which could be correlated to the chain length dependent antiaromaticity and biradical character. Our detailed studies revealed a clear structure–aromaticity–biradical character–physical properties–reactivity relationship, which is of importance for tailored material design in the future.

Infrared (IR) absorption and vibrational Raman spectra of a family of branched oligothiophenes have been determined experimentally as well as theoretically. The molecular spectra have been compared to those of the linear analogues, with identification made of spectral features due to structural properties that are valued in organic solar cell applications. The theoretical spectra have been obtained through a newly developed method in which individual conformer spectra, calculated at the time-dependent DFT level in this work, are weighted by statistics extracted from classical molecular dynamics trajectories. The agreement with experiment for the resulting averaged spectra is at least as good as, and often better than, what is observed for Boltzmann-weighted spectra. As the weights are available before the costly step of spectrum calculation, the method has the additional advantage of enabling efficient approximations. For simulating the molecular dynamics of the studied α,β-linked thiophenes and 2-methylthiophenes, high quality parameters have been derived for the CHARMM force field. Furthermore, the temperature dependence of the IR and Raman spectra has been investigated, both experimentally and theoretically.

Polycyclic hydrocarbon with a singlet biradical ground state has recently become a hot topic among various studies on π-conjugated systems and it is of importance to understand the fundamental structure–biradical character–physical properties relationship. In this work, we found that after incorporation of two additional thiophene rings into the closed-shell tetracyano-perylene (Per-CN) and quaterrylenequinodimethanes (QR-CN), the obtained new quinoidal compounds QDTP and QDTQ became a singlet biradical in the ground state due to the recovery of aromaticity of the thiophene rings in the biradical form and additional steric repulsion between the thiophene rings and the rylene unit. The ground state geometries and electronic structures of QDTP and QDTQ were systematically studied by variable-temperature nuclear magnetic resonance, electron spin resonance, superconducting quantum interference device measurements and FT Raman spectroscopy, assisted by density functional theory calculations. Both compounds were found to be a singlet biradical in the ground state with a small singlet–triplet energy gap and the biradical character was enlarged by elongation of the π-conjugation length. Strong one-photon absorption and large two-photon absorption cross-sections were observed for both compounds in the near-infrared region. Our studies demonstrated that a slight structural modification could significantly change the ground state and the electronic, optical and magnetic properties of a pro-aromatic π-conjugated system, and finally lead to new materials with unique properties. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Accepted version

In this study we designed a new class of symmetrical facial oligothiophene amphiphiles, which could be obtained in fewer steps than for previously reported analogues, but still possess the specific substituent sequence to control their backbone curvature. This novel design allows the late-stage introduction of hydrophilic groups, aiding both purification and ease of structure variation. Following the new synthetic scheme, symmetrical ter- and sexi-thiophenes were synthesized, analysed and their properties were compared to their non-symmetrical analogues. Surprisingly, the self-assembly behaviour in water, aggregate morphologies and photo-physical properties turned out to be significantly different despite the same ratio of hydrophilic and hydrophobic substituents. The new substitution pattern resulted in a drastic decrease of the critical aggregation concentration and an increase of the aggregate size. The symmetrical positioning of the substituents also heavily influenced the photo-physical properties. The changes were observed as large blue shifts in the absorption and emission spectra in water when compared to similar regio-regular oligothiophene amphiphiles.

Protein denaturation by surfactants has received increased attention in the last years due to its implications in topics such as pharmaceutics, cosmetics, paints, or biotechnology. This phenomenon is highly dependent on the physicochemical (structural) properties of the denaturing agents. In this work, we have measured for the first time the Raman optical activity (ROA) of bovine serum albumin (BSA) in the presence of three surfactants (anionic, cationic, and neutral), which has allowed us to detect new spectroscopic insights of the protein-surfactant interaction that conventional Raman spectroscopy cannot. Our work proposes two new groups of ROA marker bands to explore the unfolding of BSA induced by surfactants, which are related to "polar" (amide I and III modes) and "apolar" (methylene bending and phenyl breathing modes) protein sections. The appearance of the former groups is related to the initial attack of the surfactant, while the second groups relate to the hydrophobic unfolding.