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Two new twisted intramolecular charge transfer (TICT) donor-π-acceptor compounds were designed by combining a well-known electron acceptor naphthalimide unit with a classic electron donor dimethylaniline through two types of different rigid linkers. The combined steady-state and time-resolved spectroscopy of molecules in solvents of different polarities in comparison to solid-state solvation experiments of doped polymer matrixes of different polarities allowed distinguishing between solvation and conformation determined processes. The photophysical measurements revealed that non-polar solutions possess high fluorescence quantum yields of up to 70% which is a property of pre-twisted/planar molecules in the excited charge transfer (CT) states. The increase of polarity allows tuning the Stokes shift through all the visible wavelength range up to 8601 cm

To attain commercial viability, perovskite solar cells (PSCs) have to be reasonably priced, highly efficient, and stable for a long period of time. Although a new record of a certified power conversion efficiency (PCE) value over 25% was achieved, PSC performance is limited by the lack of hole-transporting materials (HTMs), which extract positive charges from the light-absorbing perovskite layer and carry them to the electrode. Here, we report spirobifluorene-based HTMs with finely tuned energy levels, high glass-transition temperature, and excellent charge mobility and conductivity enabled by molecularly engineered enamine arms. HTMs are synthesized using simple condensation chemistry, which does not require costly catalysts, inert reaction conditions, and time-consuming product purification procedures. Enamine-derived HTMs allow the fabrication of PSCs reaching a maximum PCE of 19.2% and stability comparable to spiro-OMeTAD. This work demonstrates that simple enamine condensation reactions could be used as a universal path to obtain HTMs for highly efficient and stable PSCs.

Carbazolyl- and 1,2,3,4-tetrahydrocarbazolyl-substituted benzothiadiazoles were prepared by Pd-catalyzed Buchwald-Hartwig and Heck reactions. Photophysical, electrochemical, thermal, charge-transporting properties, and performance in organic light emitting diodes (OLEDs) of the derivatives with donor-π-acceptor-π-donor and donor-acceptor-donor structures are discussed. Photo- and electroluminescent properties of the studied compounds of carbazole and benzothiadiazole are very sensitive to their molecular structures. Their glass transition temperatures range from 145 to 191 °C. Investigation of photophysical properties revealed importance of intramolecular twisting on excited state deactivation. Emission of dilute solutions of the compounds in nonpolar solvents appears in the orange region with fluorescence quantum yields up to 0.6.4,7-(Di (1,2,3,4-tetrahydro)carbazolyl)-[2,1,3]-benzothiadiazole demonstrates phosphorescence and delayed fluorescence at room temperature. Solid-state ionization potentials of the materials range from 5.64 to 5.82 eV. The layer of 4,7-(di (tert-butyl)carbazolyl)-[2,1,3]-benzothiadiazole shows high hole drift mobility of 1.7 × 10−3 cm2/V·s at an electric field of 5.3 × 105 V/cm and relatively high electron drift mobility of 5.7 × 10−5 cm2/V·s at an electric field of 5.8 × 105 V/cm. Red OLEDs based of singlet emission with maximum external quantum efficiency values of 1.3 and 0.13% were achieved using new emitters. Much better electroluminescent performance was observed for the compound having donor-acceptor-donor structure relative to the compound with donor-π-acceptor-π-donor structure.

Novel bipolar molecules based on naphthalene- (V555) and perylene- (V565) tetracarboxydiimide core, bearing 1-phenyl-1,2,3,4-tetrahydroquinoline end capping hole transporting groups, were designed and synthesized. Electro-optical and thermal measurements, such as UV/VIS, charge mobility, ionization potential, thermogravimetric analysis, and differential scanning calorimetry, were carried out to characterize the new materials. V555 and V565 showed bipolar behavior with both hole and electron mobilities under ambient conditions without any protection from oxygen or moisture. The gelation of V565 was observed that provides the ability to tune the charge transport properties.

The power conversion efficiency of perovskite solar cells is approaching the Shockley-Queisser limit, and therefore this technology is next to the commercialization stage. Inexpensive and stable hole transporting materials are highly desirable for the successful scale-up. Most high performing devices generally employ expensive hole conductors that are synthesized via cross-coupling reactions which require expensive catalysts, inert reaction conditions and time-consuming sophisticated product purification. In a quest to employ cost-effective chemistry to combine the building blocks, we explore enamine-based small molecules that can be synthesized in a simple condensation reaction from commercially available materials leading to an estimated material cost of a few euros per gram. The synthesized fluorene-based enamines exhibit a very high hole mobility up to 3.3 x 10(-4) cm(2) V-1 s(-1) and enable the fabrication of perovskite solar cells with a maximum power conversion efficiency of 19.3% in a doped configuration and 17.1% without doping. In addition, both PSC systems demonstrate superior long-term stability compared to spiro-OMeTAD. This work shows that hole transporting materials prepared via a simple condensation protocol have the potential to compete in terms of performance with materials obtained via expensive cross-coupling methods at a fraction of their cost and deliver exceptional stability of the final device. This work provides a design strategy for the further development of novel, low-cost semiconductors.

The influence of substituents of newly synthesized perylenediimides on their spectral properties and excited state relaxation has been studied by means of steady-state and time-resolved spectroscopy and quantum chemical calculations. Substituents at the perylene core cause broadening and shift of the absorption and fluorescence bands and also reduce the fluorescence quantum yield. Organic 4-tert-butylphenoxy substituents reduce the fluorescence yield by tens of percent by slightly reducing the oscillator strength of the radiative transition and by significantly increasing the non-radiative decay rate. We attribute both changes mainly to the distortion of the planarity of the perylene core. Bromine substituents reduce the fluorescence quantum yield by up to two orders of magnitude by opening an internal conversion channel.

Three diarylfluorene derivatives with phenyl, biphenyl, and naphthyl fragments were synthesized and characterized as electroactive materials of high thermal stability, which can form amorphous layers with glass transition temperatures of 31–74 °C. Systematic analysis of diarylfluorene compounds in the framework of the molecular charge redistribution processes according to quantum chemistry simulations allows concluding that a partially broken π-conjugated system of the core is related to the rotation motion of substituents which effectively modified the π-conjugated properties of fluorene core. The low-molar-mass derivatives, previously tested as hole transporting (HT) materials, were used in bilayer electroluminescent organic light emitting diodes with Alq3 as the emitter. The device with the HT layer of 2,7-di(1-naphthyl)-9,9-diethylfluorene exhibited the best overall performance as turn-on voltage of 4.6 V; maximum photometric efficiency of 2.8 cd A−1; maximum brightness about 7760 cd m−2.

The search for new classes of hole transporting materials (HTMs) is a very important task on the way towards commercialization of perovskite solar cells (PSCs). In this work, the synthesis and performance in PSCs of new enamine-based HTMs are presented. The synthesis scheme is very short, consisting of only one step, starting from commercially available aromatic amines. Moreover, the reaction does not require metal catalysts and is based on condensation chemistry with water as a by-product. It was shown that PSCs with such materials reach high power conversion efficiencies (PCE), with the highest PCE of 19% achieved for the V1021-based device. This work establishes enamines as a very promising class of materials for application in PSCs.

The influence of substituents on spectral properties and the excited state relaxation of indolo[3,2- b ]carbazole derivatives has been studied by means of steady-state and time-resolved spectroscopy and quantum chemical calculations. Conformational motions of the substituents in solutions were found to cause a significant acceleration of the non-radiative excited state relaxation and concomitant fluorescence quenching of the studied compounds in comparison with their solid films, where the conformational mobility is suppressed. Although the substituents also strongly influence the radiative relaxation rates, these rates are not sensitive to the conformations of the substituents.

A series of twisted-structure carbazole–fluorene tetrads featuring 3,3′-bicarbazole core decorated with singly-bonded carbazole and fluorene end-linkers were synthesized and studied as potential host materials. The tetrads inferred high glass transition temperature (up to 105 °C) and good film-forming properties, which contributed in attaining large hole drift mobilities (up to 10−3 cm2/V/s) in the solution-processed amorphous films. The revealed high triplet energies (up to 2.9 eV) indicated their potential to be utilized as hosts in blue light-emitting devices. Greater sensitivity of the triplet energies to the linking position of peripheral moieties as compared to the sensitivity of the singlets imply new possibilities for the independent tuning of these energies in carbazole–fluorene tetrads.

Owing to extended π-electron system higher polyacenes are promising materials for organic electronics, however realization of higher conjugation of acenes results in their instability under ambient conditions. We now report on synthesis, optical and electrical characterization of nitrogen heteroatom containing heptacene analogs – 8H-16,17-epoxydinaphto[2,3-c:2′,3′-g]carbazoles – decorated with various alkyl and aryl side-groups. V-shape geometry, incorporation of nitrogen heteroatom and introduced epoxy bridge ensure higher oxidative stability of the compounds as compared to analogous polyacenes. Additionally, the alteration of the molecular structure with various side-groups, either conjugated or non-conjugated, enabled the tuning of ionization potential from 4.7 eV to 5.5 eV with further gain in compound stability. This ensures of hole drift mobility up to 8 × 10−4 cm2/(V s) at 1 MV/cm for thick wet-casted films under ambient conditions. Peculiarities of forbidden lowest excited states in the V-shaped N-heptacenes are revealed based on detailed optical characterization and density functional modeling.

Cluster approach based on the multiple scattering theory (MST) formalism, realistic analytical and coherent potentials as well as effective medium approximation (EMA–CPA) can be effectively used for nanosized systems modelling. Major attention is paid now to applications of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with various morphology which possess unique physical properties in nanoelectronics, e.g. contacts of CNTs or GNRs with other conducting elements of a nanocircuit, which can be promising candidates for interconnects in high-speed electronics. The main problems connected with the resistance of C–Me junctions with metal particles appear due to the influence of chirality effects in the interconnects of single-walled (SW) and multiwalled (MW) CNTs and single-layered (SL) and multilayered (ML) GNRs with the fitting metals (Me = Ni, Cu, Ag, Pd, Pt, Au) for the predefined carbon system geometry. Using the models of ‘liquid metal’ and ‘effective bonds’ developed in the framework of the presented approach and Landauer theory, it is possible to predict resistivity properties for the considered interconnects. The model of the inter-wall interaction inside MWCNTs, which demonstrates possible ‘radial current’ losses, has been developed.

The chapter presents a short description of the main topics in non-regular nanosystems. In general, the scientific content of the discussed problems is based on the research interests of the authors of this book. Non-regularity is considered as a basic stimulus for the operational abilities of novel nanomaterials.

This chapter introduces the reader to the analysis of the structural and electronic system properties of various carbon allotropes (CNT, graphene) and several molecular derivatives. The genesis of the electronic system formation is investigated in detail. Non-regular defected nanocarbon systems are considered for possible applications in different fields, including energy storage; chemical, biochemical and electrochemical sensing; water purification; and catalysis.

The chapter presents and explains the classification of sensors in accordance with their physicochemical principles of functioning, as well as the types of recognition. Several prototypes of physical, chemical and biosensors based on polar molecular compounds such as indandione, fluorene and carbazole derivatives are described from the point of view of their structure and energy. One of the most important applications of nanosensitive materials is realized in the class of memory nanodevices. The realization of bistability in molecular or layered derivatives is usually carried out through processes based on tautomers and conformers, as well as phase transition processes. Typical examples of biomolecular rotary machines are shown. Nanotransducers principles, nanoaerogels and nanocomposites applications are also reviewed. Typical examples of biomolecular rotary machines are presented and the principles of nanotransducer operation are explained, and application of nanoaerogels and nanocomposite materials is considered.

The chapter presents functionalized CNT and GNR nanostructures as the basis for the creation of physical, chemical and biochemical nanosensors. We have shown in our simulations the sensitivity of electron conductivity of FET-type nanodevices (based on CNTs and GNRs) to local doping by nitrogen and boron. This phenomenon provides the prospective of creating nanosensors.

Physics of non-regular nanosystems is a branch of physics dealing with nanoagents – nanoparticles when non-regular nanosized morphological characteristics predetermine the nature and essence of physical phenomenon (nanophenomenon). In particular, multiple technological interfaces of nanoparticles with morphologically regular systems imply a creation of micro- or mesostructures with essential nanodimensional effects (e.g. in various schemes of functionalization of nanocarbon systems, viz. carbon nanotubes (CNTs), graphene nanoribbons (GNRs), graphene nanoflakes (GNFs), carbon-based nanoaerogels and nanofoams, etc.). However, classes of nanomaterials, in addition to nanocarbon systems, can be essentially expanded now. There are nanotube structures based on boron nitrides (BN), TiO2, chalcogenides (As-S, As-Se, As-Te, etc.) and many others. Such nanosystems should also be considered as non-regular.

Methods of numerical investigations of potentials and pseudopotentials for fundamental properties calculations (electronic, vibrational, electron-phonon phenomena, etc.) of condensed matter constitute a basic principle of modelling. It is very essential to find specific analytical approaches to the calculation of atomic and ‘crystalline’ potentials to make the calculations most effective. In particular, we pay attention to the modelling of pure Coulomb contributions and their exchange-correlation corrections in the framework of Xα- и Xαβ-approximations.

The chapter presents and explains the possibilities of CNT forest growth on Fe–Pt nanoparticles for the magnetic nanomemory. The magnetoresistance phenomena – giant magnetoresistance and tunnelling magnetoresistance (GMR and TMR) – for nanomemory devices are based on CNTs of various morphologies (i.e. various chiralities, diameters). It includes metal- and semiconductor-like CNTs which can be considered as alternative variants for electromagnetic nanosensoring and magnetic nanomemory. The chapter also presents simulations of Fe–Pt magnetically disordered nanodrops, as well as spin transport models.

The surface factor is very important for manipulating objects at a nanoscale. Thermodynamic behaviour is observed from the classical point of view, and conditional division into macro-, meso-, micro- and nano-approaches is presented. Processes of physical and chemical adsorption on the surface are presented from the energy and structure aspects. The occurrence of electronic states of the surface is presented from the classical point of view in comparison with molecular electronic states. One of the most important non-invasive optical methods to investigate nanoparticles is the surface plasmon resonance (SPR), which is quite useful for practical detection of nanoparticles in the surrounding environment. The interaction of light with nanoparticles is discussed within the framework of a nanoscale process. Nanoshells as practical implementation of nanosurface phenomena are discussed.

New emerging technologies are entering the society, which makes civil society the location for moral authority. Society is about the quality of human relationships; it is where people have to accept responsibility for the consequences of their actions; it is where the nano meets the micro and the micro meets the macro issues. Society belongs to all of us and everyone has his role to play. A new way of system thinking – nanothinking demonstrates technology trends from perfectness to non-regularity. The removal of current contradictions between regular and non-regular systems and the corresponding nanophenomena is the way to novel processes in the development of nanosciences and nanotechnologies, education and industry, consumer society and policymaking. This chapter is intended for nanomaterial consumers, managers, education practitioners, students–researchers, manufacturers, work health and safety practitioners and other interested people who do not have a background in technical sciences but who need to understand the benefits and hazards of engineered nanomaterials and require guidance on managing risks associated with these.

Nine compounds having electron-accepting 1,8-naphthalimide and electron-donating carbazole moieties were synthesized employing palladium-catalyzed C–N and C–C coupling reactions and characterized by the thermal methods, absorption and emission spectrometry, electrochemical and photoelectrical tools. The synthesized compounds possess high thermal stability with the 5% weight loss temperatures being in the range of 351–476 °C. Most of the synthesized compounds are capable of glass formation with glass transition temperatures ranging from 30 to 87 °C. The cyclic voltammetry measurements showed that the solid state ionization potentials values of the carbazole and 1,8-naphthalimide derivatives range from 5.46 eV to 5.76 eV and the electron affinities values range from −3.04 eV to −2.92 eV. Dilute solutions of the 3- and 3,6-naphthalimide-substituted derivatives of carbazole in polar solvents were found to emit in the green region with quantum yields ranging from 0.66 to 0.83, while in the solid state fluorescence quantum yields were found to be in the range of 0.01–0.45. ((E)-9-((( N -(2-ethylhexyl)-1,8-naphthalimide)-4-yl)ethenyl)-9 H -carbazole) exhibited efficient fluorescence in the solid state with quantum yield as high as 0.45. The effects of the linking topology of the chromophores and of the incorporated alkyl substituents on the thermal, optical, and photoelectrical properties of the synthesized donor-acceptor compounds are analyzed. The impact of the ground state intramolecular twisting of the carbazole and naphthalimide moieties induced by the substituents resulting in significant variation in the rates of radiative and nonradiative excitation deactivation is revealed.

Two new indan-1,3-dione and carbazole-based (IDC) compounds with single and four covalently connected chromophores were synthesized and their optical properties were investigated in solutions and in solid films with the emphasis on the interchromophore interactions. Because of molecule twisting, opening transitions to nπ* states, IDC chromophores experience ultrafast excited state relaxation with the time constant of about 2 ps in solutions and several times slower solid films. Chromophore connection into quadruplicate molecules only weakly influence their spectroscopic properties in solutions, however prevents H-type aggregate formation and concomitant spectral changes in solid films.

A synthetic route to a series of anthracene derivatives consisting of 2-phenylanthracene and its conformationally-stabilized planar derivatives, containing carbon, oxygen, sulphur and nitrogen atoms, is reported. Thermal, optical and electrical properties of the derivatives featuring an extended π-conjugated electron system were also investigated. Experimental results were supplemented by the energy spectra and molecular orbital calculations performed in the framework of density functional theory. Some of the compounds were found to be molecular glasses with glass transition temperatures from 28 to 55 °C as revealed by differential scanning calorimetry. The anthracene compounds in dilute solutions were found to emit in the 400–500 nm wavelength range with the fluorescence quantum yields varying from 0.22 up to 0.46. The solid films of the anthracene derivatives exhibited slightly narrower emission wavelength-tunability with clearly-expressed excimer emission bands (for the benzothiophene- and indole-anthracene compounds) causing a significant lowering of the fluorescence quantum efficiency down to 0.005. Rigidity of the studied anthracene molecules was assessed by evaluating the Huang-Rhys factor (indicating strength of electron-vibrational coupling) from the vibronic profile of the fluorescence spectra, which indicated that the cyclized indole- and benzofuran-anthracenes possess the most rigid molecular structures as opposed to more flexible structures of 2-phenylanthracene and indeno-anthracene. Wet-casted films of the anthracene compounds demonstrated moderate charge carrier drift mobilities, in the order of 10 −5 –10 −4 cm 2 /V, which are considered as sufficient for light-emitter applications. Moreover, introduction of additional C, O, S and N atoms into 2-phanylanthracene molecule enabled a tuning of the HOMO level from 4.9 up to 5.74 eV, which is crucial for the optimization of hole injection into the active layers, and thus for balancing electron and hole currents in light-emitting devices.

New pyrenyl mono- and disubstituted fluorene and carbazole derivatives were synthesized and investigated as blue-emitting materials. Most of the synthesized compounds were capable of forming glasses with glass transition temperatures up to 105 °C. The mono- and disubstituted compounds exhibited efficient emission in a diluted form with the peak wavelengths of 416 and 422 nm and quantum yields of 0.72 and 0.82, respectively. Photophysical properties of the compounds in dilute solutions and solid state were investigated experimentally and rationalized by density functional theory calculations. The calculations revealed a low energy barrier for intramolecular twisting in the ground and excited states. The electronic spectra of the compounds were dominated by an allowed “pyrene-like” S0 → S2 transition prevailing in nearly perpendicularly twisted molecular structures and competitive S0 → S1 transition becoming increasingly allowed for more planar conformers. The disubstituted compounds demonstrated a 3-fold e...

Synthesis and properties of new glass-forming 2-, 2,7-substituted carbazole dimers and trimers exhibiting ambipolar charge carrier transport are reported. The results of thorough evaluation of thermal, optical, and photoelectrical properties of the carbazole derivatives are presented. Additionally, a comparative experimental and theoretical analysis of the 2,7-substituted carbazole trimer with the 3,6-substituted analogue is performed. 2,7-Di(9-carbazolyl)-9-(2-ethylhexyl)carbazole was found to show very high electron mobility (μe = 2 × 10−3 cm2 V−1 s−1 at an electric field of 1.8 × 105 V/cm) and reasonably high hole mobility (μh = 8 × 10−4 cm2 V−1 s−1 at an electric field of 1.8 × 105 V/cm). 2-Substituted carbazole dimers also demonstrate bipolar conductive properties although with significantly lower charge carrier mobility values. The obtained carrier mobility values for the 2,7-substituted carbazole compound were found to be nearly 2 orders of magnitude higher than those for 3,6-substituted carbazole ...

Ozonization reaction of simple alkenes was studied by means of FT infrared absorption gas spectroscopy. The reaction was performed at 95 K in neat films of the reactants. IR absorption spectra of the gaseous products were recorded. The spectra were analyzed combining experimental results with theoretical calculations performed at B3LYP 6-311++G (3df, 3pd) level. We found that among all theoretically predicted conformers of propene secondary ozonide, only one which has the O-O half-chair configuration for the five membered ring and the radical attached in the equatorial position was present in the sample. Samples of 1-butene and 1-heptene secondary ozonides consist from two conformers of very similar energy (ΔH=0.3 kJ/mol). The most stable conformer for both ozonides is the one with O-O half-chair configuration of the five membered ring and the radical attached in equatorial position and the aliphatic chain in gauche position. The second stable conformer has the aliphatic chain in anti position.

Infrared spectra of 1,1,1-trifluoropropyltrifluorosilane (CF3CH2CH2SiF3) were obtained in the vapour, amorphous and crystalline solid phases in the range 4000–50 cm−1. Additional spectra in argon and nitrogen matrices at 4.8 K were recorded before and after annealing to temperatures of 20–36 K. Raman spectra of the compound as a liquid were recorded at various temperatures between 298 and 163 K and spectra of the amorphous and crystalline solids were obtained. The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the vapour was shock-frozen on a cold-finger at 78 K and subsequently annealed to 120–150 K, 12 mostly weak Raman bands vanished in the crystal. Much smaller variations were observed in the corresponding infrared spectra after annealing. However, the spectra indicated the existence of two different crystals, formed after annealing the amorphous solid to 120 and to 150 K; both crystals contained the same conformer (anti). Raman and IR spectra of 1,1,1-trifluoropropyltrifluorosilane in cyclohexane, carbon tetrachloride and acetonitrile revealed conformational displacements with solvent polarity. From intensity variations between 298 and 223 K of the Raman pair 639/665 cm−1, ΔH° (gauche–anti) = 3.4 ± 0.3 kJ mol−1 was obtained in the liquid. Annealing experiments indicate that the anti conformer also has a lower energy in argon and nitrogen matrices; moreover, the low-energy conformer is present in the crystal. The spectra of both conformers have been interpreted in detail. Ab initio calculations at the HF/6–311(d), HF/6–311 G (3df,3pd) and MP2/G–31(d) levels gave optimized geometries, infrared and Raman intensities and scaled vibrational wavenumbers for the anti and gauche conformers. The conformational energy difference derived was 5.3 kJ mol−1 with anti being the low-energy conformer. Copyright © 2003 John Wiley & Sons, Ltd.

The Raman spectrum of liquid ethyldibromosilane, CH3CH2SiHBr2, was recorded at various temperatures between 298 and 218 K, and the spectrum of the crystal was obtained at 210 K from a sample sealed in a capillary. Additional spectra of the amorphous and annealed crystals, which were deposited on a copper finger cooled with boiling liquid nitrogen, were recorded. The infrared spectra were recorded of the vapor and amorphous and crystalline solid in the range 4000–50 cm−1 and mid-infrared spectra isolated at 4.8 K in argon and nitrogen matrices were also observed. These vibrational spectra show that two conformers, anti and gauche, are present in the vapor and in the liquid, but only the anti conformer remains in the crystalline solid. Three conformer pairs in the Raman spectrum of the liquid phase were used to obtain the enthalpy difference, which gave an average value of 128 ± 17 cm−1 (1.53 ± 0.2 kJ mol−1) with the anti form lower in energy. At ambient temperature it is estimated that there is 52 ± 2% of the gauche conformer present in the liquid. The optimized geometries, infrared and Raman intensities, and scaled vibrational wavenumbers for the anti and gauche conformers were obtained from ab initio MP2/6–31G(d) calculations with full electron correlation. The conformational energy difference was also obtained from ab initio MP2/6–311 + G(d,p) calculations which gave a predicted energy difference of 97 cm−1 with the anti form the conformer of lower energy. These spectroscopic and theoretical results are discussed and compared with the corresponding quantities for some similar molecules. Copyright © 2003 John Wiley & Sons, Ltd.

Ethyl iodosilane (CH 3 CH 2 –SiH 2 I) was synthesized for the first time. Infrared spectra were recorded in the vapour, amorphous and crystalline solid phases in MIR and FIR regions. Additional MIR spectra of the compound isolated in argon and nitrogen matrices were obtained at 5 K. Raman spectra of the liquid, excited by argon and by Nd 3+ YAG lasers, were recorded at room temperature including polarization measurements. The spectra were studied in an extended temperature range 173–353 K and a Δ H value of 1.2±0.3 kJ mol −1 was obtained with gauche being the low energy conformer. Spectra of the amorphous and crystalline solids were obtained at liquid nitrogen temperature. Ethyl iodosilane exists in an equilibrium between anti and gauche conformers, in the vapour, liquid and amorphous states. After careful annealing the amorphous solid on a cold Cu finger (Raman) or on a CsI or Si window (infrared) to 160 K a partly crystalline solid was formed. A number of IR and Raman bands were reduced in intensity after annealing, although they did not vanish completely. From comparison between the observed and calculated vibrational modes it was apparent that the gauche conformer was present in the crystal. The sample was mixed with argon and nitrogen in a ratio 1:1000, deposited on a window at 5 or 10 K and annealed to temperatures between 5 and 36 K (argon) and 5–30 K (nitrogen). IR bands attributed to the anti and gauche conformers were reduced and increased in intensities, respectively. Thus, the gauche conformer was the low energy conformer in the matrices and probably also in the vapour phase. Ab initio calculations were performed at the RHF/3-21 G* and 6-311G* B3LYPs and gave optimized geometries, IR and Raman intensities and vibrational frequencies for the anti and gauche conformers. An enthalpy difference of 0.9 kJ mol −1 was obtained from the calculations with gauche being the low energy conformer. After scaling, a reasonably good agreement between the experimental and calculated wavenumbers for the anti and gauche conformer was obtained. The spectra of ethyl iodosilane were closely related to those of the corresponding ethyl fluoro, ethyl chloro and ethyl bromosilane.

The infrared spectra of ethyl bromosilane, CH 3 CH 2 SiH 2 Br and the Si-d 2 isotopomer, were recorded in the vapor, amorphous and the crystalline solid phases in the range 4000–400 cm −1 . The mid-infrared spectra of the ‘light’ compound, isolated at 4.8 K in the argon and the nitrogen matrices were also observed. Raman spectra of the liquids were recorded at various temperatures between 298 and 218 K, and the spectrum of the crystal was obtained from a sample sealed in a capillary at 210 K. Additional spectra of the amorphous and annealed crystals, which were deposited on a copper finger cooled with liquid nitrogen, were recorded. These vibrational spectra show that two conformers— anti and gauche —are present in the vapor and in the liquid, but only the gauche conformer remains in the crystalline solid. Six conformer pairs in the liquid phase were used to obtain the enthalpy difference which gave an average of 140±25 cm −1 (1.67±0.3 kJ/mol) with gauche form lower in energy. Additionally variable temperature (−120 to −155 °C) studies of the infrared spectra of the sample dissolved in liquid krypton have been carried out and the enthalpy difference has been determined to be 130±13 cm −1 (1.56±0.16 kJ/mol), again with the gauche conformer the more stable form. At ambient temperature it is estimated that there is 22±2% of the anti conformer present. The optimized geometries, infrared and Raman intensities, and scaled vibrational frequencies for the anti and gauche conformers were obtained from ab initio MP2/6-31G(d) calculations. The conformational energy difference was also obtained from ab initio MP2/6-311+G(d, p) calculations which gave a predicted energy difference of 129 cm −1 with the gauche form the lowest energy. From the isolated Si–H stretch frequencies from the Si-d 1 isotopomer the Si–H distances were determined to be 1.481 and 1.480 A for the gauche and anti conformers, respectively. The spectroscopic and theoretical results are discussed and compared to the corresponding quantities for some similar molecules.

Chloromethyl methyl dichlorosilane (ClCH2CH3SiCl2) was synthesized and the infrared spectra of its vapour, and of the amorphous and crystalline states, cooled to the temperature of liquid nitrogen were recorded. Additional mid IR spectra of the compound, isolated in both argon and nitrogen matrices, were taken at 5 K. Raman spectra of the liquid were recorded in a capillary at various temperatures between 298 and 223 K. The crystal was also studied in a capillary at 210 K and deposited onto a copper finger cooled with liquid nitrogen. The compound occurs as anti and gauche conformers in its vapour and liquid states. Approximately five Raman bands, some of them weak, present in the fluid phases vanished upon crystallization. An additional eight IR bands disappeared or were reduced in intensity after crystallization. Two band pairs in the Raman spectra were used to calculate the enthalpy difference between the conformers in the liquid phase giving a value: ΔH(liq)(anti–gauche) of 0.0(±0.4 kJ mol−1. In the argon and nitrogen matrices, various small intensity variations in the IR bands were observed after annealing to ca. 36 K (argon) or 32 K (nitrogen). The gauche bands generally increased and the anti bands decreased in intensity, suggesting that gauche has a lower energy in the matrices. The conformational barrier was estimated to be 8–10 kJ mol−1. The optimized geometries, infrared and Raman intensities, and scaled vibrational frequencies for the anti and gauche conformers were derived from ab initio calculations at the RHF/6-311G∗level. The derived conformational energy difference was 7.2 kJ mol−1, gauche being the conformer of lowest energy. The calculated dipole moments of the anti and gauche conformers were 4.2 and 2.0 D, respectively. Correlation between the observed and calculated wave numbers of both conformers revealed that gauche was present in the crystal, and assignments of the spectra have been carried out.

Nitrous oxide (N2O) plays an important role in greenhouse warming and ozone depletion. Yung and Miller's zero point energy (ZPE) model for the photolysis of N2O isotopomers was able to explain atmospheric isotopomer distributions without invoking in situ chemical sources. Subsequent experiments showed enrichment factors twice those predicted by the ZPE model. In this article we calculate the UV spectrum of the key N2O isotopomers to quantify the influence of factors not included in the ZPE model, namely, the transition dipole surface, bending vibrational excitation, dynamics on the excited state potential surface, and factors related to isotopic substitution itself. The relative cross-sections are calculated as the Fourier transform of the correlation function of the initial vibrational wave function and the time-propagated wave function, using a Hermite expansion of the time evolution operator. The model uses the electronic structure data recently published by Balint-Kurti and co-workers and makes severa...

Infrared spectra of 2-chloroethyl trifluorosilane (CETFS) (ClCH2CH2SiF3) were obtained in the vapour, amorphous and crystalline solid phases in the range 4000–50 cm−1. Additional variable temperature spectra in liquefied xenon and spectra in argon and nitrogen matrices at 5 K were recorded. Raman spectra of the compound as a liquid were recorded at various temperatures between 298 and 180 K and amorphous and crystalline solids were obtained. The spectra of CETFS revealed the existence of two conformers (anti and gauche) in the vapour and in the liquid. Large variations in the infrared and Raman spectra were observed when the vapour was shock-frozen on a window at 80 K and subsequently annealed. An intermediate phase appeared at ca. 125 K containing both conformers. A crystal was formed at 160 K, and ca. 18 infrared and/or Raman bands present both in the fluid phases and in the 125 K solid vanished in this crystal. From the intensity variations between 293 and 183 K of four Raman band pairs, Δ H 0 (anti−gauche)=0.8±0.3 kJ mol −1 was obtained in the liquid. In liquid xenon under pressure a ΔH value of −0.7±0.1 kJ mol−1 was calculated from the intensity variations between 218 and 173 K of two band pairs in the infrared spectra. Annealing experiments indicate that the anti conformer has slightly lower energy in argon and nitrogen matrices. Also, the anti conformer has the lower energy in liquid xenon, whereas the more polar gauche rotamer is the low energy conformer in the liquid and is also present in the crystal. The spectra of both conformers have been interpreted in detail. Ab initio calculations were performed using the gaussian 94 program with the HF/6-311G∗ basis set and gave optimized geometries, infrared and Raman intensities and scaled vibrational frequencies for the anti and gauche conformers. The conformational energy difference derived was 3.8 kJ mol−1 with anti being the low energy conformer.

A high resolution FTIR study of intermolecular interactions in van der Waals dimers, HCl–ethylene and HCl–acetylene, has been carried out. Partly resolved vibration–rotation spectral bands of the complexes are observed in the spectral region 2795–2820 cm−1. Assignments of the vibrational spectral bands are made combining ab initio data with the experimental results. It is concluded that the very unsymmetrical shape of the P branches of A-type bands is due to an increase of the rotational constants B and C in the first vibrationally excited state of the HCl stretch of the complexed HCl. The ab initio calculations predict the existence of low wavenumber intermolecular fundamental vibrations whose first excited states have significant populations at the temperatures of the measurements. Hot bands due to these fundamentals have been observed in the spectra.

The infrared (IR) spectra of dichloromethylmethyl dichlorosilane (Cl2CHCH3SiCl2) were recorded in the vapor, amorphous and partly crystalline phases between 4000 and 50 cm−1. IR spectra (4000–450 cm−1) of the compound were also obtained when isolated in argon, nitrogen and krypton matrices at 4.8 K before and after annealing to temperatures in the range 15–50 K. Raman spectra of the liquid were recorded at various temperatures between 295 and 147 K. Spectra of the amorphous and annealed crystal deposited on a copper finger at 78 K were obtained. The spectra showed the existence of two conformers — anti and gauche — in the vapor and in the liquid. Approximately 12 IR bands were reduced in intensity and 6 Raman bands present in the fluid phases vanished upon crystallization. From the intensity variations of two band pairs with temperature, a ΔH0 value of 0.4±0.3 kJ mol−1 between the conformers was obtained in the liquid, anti being the low-energy conformer. Small increases and decreases in the IR band intensities were observed in the matrix spectra after annealing to 32 (nitrogen), 36 (argon) and 50 K (krypton). The enthalpy difference between the conformers is low in the matrices, but the anti conformer had lower energy than the gauche. Ab initio calculations were performed using the Gaussian -94 program with the RHF/6-311G∗ basis function and gave optimized geometries, IR and Raman intensities and scaled vibrational frequencies for the anti and gauche conformers. The conformational energy derived was 4.4 kJ mol−1 with anti being the low-energy conformer. The dipole moments were calculated to be 1.2 and 3.1 debye for the anti and gauche conformers, respectively. Correlation between the observed and calculated wavenumbers of both conformers revealed that anti was present in the crystal, and complete assignments of the spectra have been carried out.

The infrared spectra of dichloromethylmethyldichlorosilane (Cl2CHCH3SiCl2) were recorded in the vapour, amorphous and partly crystalline phases and when isolated in argon, nitrogen and krypton matrices at 5 K. Raman spectra of the liquid were recorded at various temperatures between 295 and 147 K. Spectra of the amorphous and annealed crystal deposited on a copper finger at 80 K were obtained. The spectra showed the existence of two conformers, anti and gauche, in the vapour and in the liquid. Approximately 12 infrared bands were reduced in intensity, and six of the same bands present in the fluid phases in the Raman spectra vanished upon crystallization. From the intensity variations of two band pairs with temperature, a 1H ◦ value of 0.4 ± 0. 3k J mol −1 between the conformers was obtained in the liquid, anti being the low-energy conformer. Small increases and decreases in the IR band intensities were observed in the matrix spectra after annealing to 32 K (nitrogen), 36 K (argon) and 50 K (krypton). The enthalpy difference between the conformers is low in the matrices, but the anti conformer had lower energy than the gauche conformer. Ab initio calculations were performed at the HF/6‐311G ∗ level and gave optimized geometries, vibrational wavenumbers and infrared and Raman intensities for the anti and gauche conformers. The conformational energy derived was 4.4 kJ mol −1 with anti being the low-energy conformer. The dipole moments were calculated to be 1.2 and 3.1 D for the anti and gauche conformers, respectively. Correlation between the observed and calculated wavenumbers of both conformers revealed that anti was present in the crystal, and complete assignments of the spectra were carried out. Copyright  2001 John Wiley & Sons, Ltd.

International audience; The excitation decay kinetics of polar Indandione-1,3 Pyridinium Betaine (IPB) molecules in various environments: solvents, films and crystals, were studied using time-resolved luminescence and transient absorption measurements. A red-shift, depolarization and fast decay of the luminescence intensity were observed on a femtosecond time scale in dilute solutions and explained by excitation relaxation from the initially created intramolecular charge transfer state to the lower energy excited state of the indandione moiety. The first fast relaxation stage is followed by a slower one responsible for the relaxation to the ground state stage with the rate depending on the viscosity of the surrounding. By comparing the excitation properties of IPB in solution and those in the crystal form, the influence of the intermolecular interactions on the excited state dynamics is revealed. Excitation relaxation in the IPB deposited films of different thickness and in a single crystal is described as a competition between different relaxation paths of nonradiative recombination, these paths being the high lying Frenkel exciton states and the low lying intermolecular charge transfer states.

The Raman spectra (3500–20 cm−1) of liquid with depolarization values and solid, as well as the infrared spectra of the gas, the sample isolated in argon and nitrogen matrices at ca. 5 K and solid dimethyl vinyl fluorosilane, CH2 CHSi(CH3)2F, have been recorded. Both gauche and syn rotamers have been identified in the fluid phases but only the syn conformer remains in the solid. Variable temperature (−55 to −150°C) studies of the infrared spectra (4000 and 400 cm−1) of dimethyl vinyl fluorosilane dissolved in liquid xenon and krypton have been recorded. From the xenon and krypton data, the enthalpy differences have been determined to be 53±9 cm−1 (0.64±0.10 kJ/mol) and 44±7 cm−1 (0.53±0.09 kJ/mol), respectively, with the gauche conformer being the more stable form. The intensity variations with temperature of the Raman spectrum of the liquid gave an enthalpy difference of 25±15 cm−1 (0.30±0.18 kJ/mol) also with the gauche conformer being the more stable form. Vibrational assignments are provided for both conformers. Complete equilibrium geometries have been determined for both rotamers using ab initio calculations employing the 6-31G(d), 6-311+G(d,p) and 6-311+G(2d,2p) basis sets at the levels of restricted Hartree–Fock (RHF) and/or with full electron correlation by the perturbation method, Moller–Plesset (MP), to second order. The syn conformer is predicted to be the more stable conformer from all ab initio calculations except those of MP2/6-31(d) which predict the gauche form being the more stable conformer by 54 cm−1 (0.65 kJ/mol) although the values favoring the syn form are all very small. These results are compared to the corresponding quantities of some similar molecules.

Chloromethylmethyldifluorosilane (CH2ClCH3SiF2) was synthesized for the first time. Raman spectra of the liquid were recorded at various temperatures between 298 and 175 K and spectra of the amorphous and crystalline solids were obtained. Infrared spectra were recorded in the vapour, amorphous and crystalline solid phases in the MIR and FIR regions. Additional MIR spectra of the compound isolated in argon and nitrogen matrices were obtained at 10 K. The spectra of chloromethylmethyldifluorosilane showed the existence of two conformers, anti and gauche, present in the vapour and in the liquid. By careful annealing the amorphous solid formed by depositing the vapour on a cold Cu finger (Raman) or on CsI or silicon windows (infrared) at 80 K, two different crystals were formed. One of these, obtained after annealing to 125 K (crystal I), contained the anti conformer; the other, achieved after annealing to ca 170 K (crystal II), contained molecules in the gauche conformation. If the liquid was cooled, crystal II was formed, suggesting this crystal to be stable, whereas crystal I appeared to be metastable. The anti and gauche conformers had approximately the same enthalpy in the liquid, giving a negligible ΔH (gauche–anti) equal to 0.2 ± 0.4 kJ mol−1, but gauche was the conformer of the stable crystal II. Intensity variations in the matrix spectra after annealing indicated that gauche was the low-enthalpy conformer in both matrices and probably also in the vapour. These experimental data make a very reliable assignment of the conformer bands possible. Ab initio calculations were performed at the HF/6–311G* level, from which optimized geometries, infrared and Raman intensities and scaled vibrational wavenumbers for the anti and gauche conformers were obtained. The conformational energy derived was 5.9 kJ mol−1, with gauche being the low-energy conformer. Copyright © 2000 John Wiley & Sons, Ltd.

The infrared spectra of 1,1,1-trifluoropropyl trifluorosilane were recorded in the vapour, amorphous and crystalline solid phases in the range 4000–50 cm −1 . Additional MIR spectra of the compound isolated in argon and nitrogen matrices at 5 K before and after annealing to temperatures in the range 15–35 K were obtained. Raman spectra of the liquid were recorded at various temperatures between 298 and 163 K. Spectra of the amorphous solid on a copper finger were recorded and spectra of crystalline solids cooled by different techniques were obtained. The spectra showed the existence of two conformers – anti and gauche – present in the vapour and in the liquid. Approximately five Raman bands present in the fluid phases vanished upon crystallization, but only small changes occurred in the corresponding infrared spectra. From intensity variations with temperature in the Raman spectra of the liquid, the enthalpy difference was determined to be ΔH(gauche-anti)=3.2 kJ mol −1 . Ab initio calculations were performed using the Gaussian 94 program with the HF/6-311G* basis set and gave optimized geometries, infrared and Raman intensities and scaled vibrational frequencies for the anti and gauche conformers. The conformational energy was calculated to be 5.3 kJ mol −1 with anti being the low energy conformer.

Ethyl bromosilane (CH 3 CH 2 SiH 2 Br) and ethyl dibromosilane (CH 3 CH 2 SiHBr 2 ) were synthesized and their infrared and Raman spectra determined in vapour (IR), liquid (Raman), amorphous solid, and crystalline states. Additional infrared spectra of the compounds isolated in argon and nitrogen matrices at 5 K were recorded before and after annealing to temperatures in the range of 15–35 K. Raman spectra of the liquid were recorded at various temperatures between 295 and 153 K. Both the spectra showed the existence of two conformers – anti and gauche – present in the fluid and amorphous phases. The crystals contained the gauche conformer for bromide and anti conformer for the dibromide in accordance with the results for the chloro and iodo homologues. The enthalpy differences in the liquids measured in Raman gave: Δ H (anti-gauche) = 1.8 ± 0.3 and Δ H (gauche-anti) = 2.1 ± 0.3 kJ mol −1 , respectively. Ab initio calculations were performed using the Gaussian 94 program with the HF/6-311G* basis set and gave optimized geometries, infrared and Raman intensities and scaled vibrational frequencies for the anti and gauche conformers. The conformational energies were calculated to be 0.02 kJ mol −1 for ethyl bromosilane and 0.3 kJ mol −1 for ethyl dibromosilane with the anti and gauche conformers having the lower energy, respectively.

Nonradiative excited-state relaxation via charge transfer induced twisting of N,N-dimethylaminobenzylidene-1,3-indandione (DMABI) in solution was investigated by means of picosecond transient absorption and femtosecond fluorescence spectroscopy.The analysis of the experimental data allows us to distinguish between different reaction stages of the molecular twisting in excited and ground states, as well as to consider the molecular dynamics along reactive (twisting) and nonreactive (solvation) coordinates. Quantum chemical calculations of the electronic structure of DMABI and its dependence on the molecular conformation are discussed in order to identify the bond(s) involved in the twisting reaction. It is found that such a twisting bond is the CC double bond, which is substantially weakened in the excited state.

The origin of exciton states in crystals built up by dipolar N,N-dimethylaminobenzylidene 1,3-indandione (DMABI) molecules has been investigated by means of absorption and luminescence spectroscopy. The exciton spectral and dynamical properties in the solid state are compared to those of the excitation of separated DMABI molecules embedded in a rigid polymer matrix. The luminescence excitation spectra and the luminescence decay kinetics are discussed on the basis of the specific adiabatic potential-energy scheme of the self-trapped excitons.

A novel non-linear fluorescence (NLF) effect in polar dimethylaminobenzylidene 1,3-indandione (DMABI) crystals is presented and discussed. A single crystal or vacuum-evaporated layer of DMABI excited in the IR region at 1064 nm (by a Q-switched YAG laser) emits red light in the visible region of the spectrum at 600–740 nm depending on the DMABI crystalline modification. This anti-Stokes luminescence shows a quadratic dependence on the exciting light intensity which transforms to a linear dependence at very high excitation intensities. The observed NLF effect under IR excitation is determined by optical transitions into intermolecular charge transfer (CT) states. It has been suggested that the photoexcited singlet 1CT excitations may either interact in a quadratic singlet–singlet (1CT + 1CT) annihilation reaction or, more probably, form long-lived triplet 3CT excitons via a hyperfine interaction effect which may subsequently annihilate in a similar bimolecular fusion reaction (3CT + 3CT). In both cases the excited molecular singlet state S1 is formed and thus the NLF effect is due to singlet–singlet or triplet–triplet fusion of CT excitons. A detailed energy diagram and kinetic description of the model are presented. Quantum chemical calculations of the electronic structure of the DMABI molecule illustrate the dipolar nature of its ground and excited states.