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Modeling of cationic and excited states of boron difluoride acetylacetonate and eight of its γ-substituted derivatives was carried out using the methods of outer-valence Green's functions (OVGF), algebraic-diagrammatic construction for the polarization propagator of the second order (ADC(2)), coupled clusters with single and double excitations (EOM-CCSD), and time-dependent density functional theory (TDDFT/CAMB3LYP). Comparison of the calculated data with the absorption spectra made it possible to determine the influence of functional groups on the energies of electronic transitions and the nature of the absorption spectrum bands. Addition of the substituent SPh causes a decrease in the energy gap between the levels of the highest occupied and lowest vacant molecular orbitals, which determine the bathochromic shift of the long-wavelength band in the absorption spectrum relative to the other studied complexes. In the complexes containing Cl, Br, SCN, SEt, SPh and OS(O)2Ph groups in the γ-position, it was found that the highest occupied molecular orbitals are localized mainly on the substituents, and the lowest vacant molecular orbital corresponds to the chelate orbital π4, which determines the presence of transitions with charge transfer. It was shown that the calculated energies of excited states according to the ADC(2) method, in comparison with EOM-CCSD and TDDFT/CAMB3LYP, can be correlated with maxima of the experimental absorption spectra for the lowest average shift (0.27 eV).

The ground (S(0)) and excited triplet (T(1)) electronic states and corresponding optical spectra of a series of cationic complexes [RuH(CO)L(PPh(3))(2)](+) (L=2,2´-bipyridyl) (Rubpy), 4,4´-dicarboxylic-2,2´-bipyridyl (Rudcbpy), bis-4,4’-(N-methylamide)-2,2´-bipyridyl (Rudamidebpy), bis-4,4’-(methyl)-2,2´-bipyridyl (RudMebpy), [Ru(CO)(2)dcbpy(PPh(3))(2)](2+) (Ru(2CO)dcbpy), and [Ru(H)(2)dcbpy(PPh(3))(2)] (Ru(2H)dcbpy) have been studied by combined Density Functional/Time-Dependent Density Functional (DFT/TDDFT) techniques using different combinations of DFT exchange-correlation functionals and basis sets. PBE0/LANL2DZ provided more accurate geometries to describe S(0) whereas B3LYP/LANL2DZ predicted spectral energies that correlated better with the available experiment data. The Ru (II) complexes with different substituents emit photons ranging from 560–610 nm in the series RudMebpy, Rubpy, Rudamidebpy, Rudcbpy. The calculations predicted a maximum emission at about 540 nm for the complex constructed from two carbonyl π-acceptors ligands trans to the dcbpy, while an emission in the far infrared region is calculated when two H σ-donor ligands trans to the dcbpy. Our calculation results show correlations between HOMO-LUMO energy gap, Stokes shift, and T(1) distortion, which reflect the different effects of electron-withdrawing and donating groups. We proposed that these correlations can be used to predict the photophysical properties for new complexes.

The coordinative bonding interaction involving glycine ligand with three randomly, selected transition metals ions chromium, nickel and titanium is analysed using standard perturbation principles. The experimental data is collected by accurately measuring the spectral shifts or relative strengths of perturbations from corresponding electronic spectra of the solution complexes and through supportive DFT calculations using some innovative approaches. The observed spectral shifts are interpreted as glycine ligand perturbations on the appropriate excited electronic state of the transition metal ion following coordinative bonding interaction. The neighbouring excited but unperturbed states including the ground state facilitate the redistribution of the perturbation energy within the manifold of the transition metal ion electronic energy states. The information allows for a detailed new insight into the intrinsic mechanism of coordinative bonding interaction.

Made available in DSpace on 2019-10-04T12:38:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-09-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The solvent-induced Stokes' shift, which describes the response at different solvents (acetonitrile, chloroform, dichloromethane, 1,4-dioxane, N,N-dimethylformamide, ethanol, heptanol, tetrahydrofuran, and toluene) to a sudden change in the charge distribution of excited 4-(Dicyanomethylene)-2-tert-butyl-6- (1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) molecule, was studied through absorption and emission spectra and TD-DFT calculations; the solvent effect was studied trough the IEF-PCM model. The application of IEF-PCM model with TD-DFT methods to obtain the absorption energies provided excellent match with the experimental results. The results observed, for solvents effects on the positions of maxima absorption and emission between experimental data and theoretical calculations, have average absolute deviations of only 0.03 eV and 0.22 eV, respectively. A systematic error was observed by comparing the theoretical and experimental maxima for the emission energies. However, the application of the Lippert-Mataga and Bilot-Kawski equations to the TD-DFT-simulated Stokes' shifts values resulted in excellent correlation coefficients: Lippert-Mataga, R-2 = 0.9982, Bilot-Kawski, R-2 = 0.9908 and R-2 = 0.9795. (C) 2019 Elsevier B.V. All rights reserved. Univ Estadual Campinas, UNICAMP, Inst Chem, Dept Phys Chem, BR-13083861 Campinas, SP, Brazil Sao Paulo State Univ, UNESP, Fac Sci, Dept Chem, BR-17033360 Bauru, SP, Brazil Sao Paulo State Univ, UNESP, Fac Sci, Dept Chem, BR-17033360 Bauru, SP, Brazil FAPESP: 2016/20549-5 FAPESP: 2015/22338-9 FAPESP: 308480/2016-3 FAPESP: 2016/04963-6 FAPESP: INCT.Bio.Nat 2014/50926-0 CNPq: 302793/2016-0 CNPq: 306975/2013-0 CNPq: 305541/2017-0 CNPq: 440503/2014-0

Two free base meso-tetraphenylporphyrin-fullerene dyads, H2PMe-C60, H2POMe-C60, and their zinc complexes, ZnPMe-C60 and ZnPOMe-C60, which the para positions of the meso-tetrasubstituted phenyl groups of the porphyrin core were substituted by methyl(-Me) and methoxyl(-OMe) groups respectively, were synthesized. The porphyrin unit in the synthesized dyads is directly linked to the fullerene entity through the pyrrole-β- position rather than through the traditionally meso-substituted phenyl group, which may be more favorable for electron communication between the donor and the acceptor. They are fully characterized by mass spectrometry, nuclear magnetic resonance, infrared spectroscopy and ultraviolet visible spectroscopy. Experimental results obtained from steady-state fluorescence spectroscopy and cyclic voltammetry show that the coordination of the zinc ions lead to an increase in the singlet excited state energy of the metallated porphyrin unit by about 0.15 eV, and to a reduce in the HOMO level and in the HOMO-LUMO energy gap. The molecular reorganization energy decreases after the electron-donating groups of -Me or -OMe attaching to the para position of the meso-phenyl group of the porphyrin moiety. The results of the energy calculations show that photoinduced electron transfer is thermodynamically favorable for the synthesized porphyrin-C60 dyads. There exists a competition between the photoinduced electron transfer and energy transfer processes from the first singlet excited state of porphyrin core to fullerene moiety. The photoinduced electron transfer rate constant of the dyads were calculated according to Marcus theory. The results indicate that the coordination of metal zinc ions lead to great increase in the electron transfer rate constant. Further, the photoinduced electron transfer rate constant increases in the order ZnP-C60, ZnPMe-C60, ZnPOMe-C60.

In the present studies, synthesis of two novel benzofuran-3-acetic acid hydrazide derivatives namely, (6-methyl-benzofuran-3-yl)-acetic acid hydrazide [6MLBH] and (6-methoxy-benzofuran-3-yl)-acetic acid hydrazide [6MOBH] are reported. The probes are characterized by IR, 1H-NMR, 13C-NMR and mass spectral methods. The absorption and fluorescence maxima of novel derivatives 6MLBH and 6MOBH are determined for different solvents of varying polarity and the solvatochromic behavior and dipole moments are investigated. Stoke's shift exhibits a red shift with increase in solvent polarity for both the probe molecules indicating a π→π* transition. The ground state dipole moment (μg) of both the molecules in gaseous phase is estimated from ab initio computations by using Gaussian 09 W software and also from solvatochromic method and the results are compared. Further, the ground state dipole moments of the probe molecules in different solvents were also estimated theoretically by using the integral equation formalism of polarizable continuum model (IEF-PCM). By using solvatochromic correlations like Lippert's, Bakhshiev's, Kawski-Chamma-Viallet's and solvent polarity parameter ( E T N ) , the excited state dipole moments (μe) are determined. Results show that, the excited state dipole moments (μe) are higher than the ground state dipole moments (μg) and suggest that, the probe molecules 6MLBH and 6MOBH are more polar in the excited state. The HOMO-LUMO energy gaps computed from density functional theory (DFT) and from absorption threshold wavelengths are found to be in agreement and also support intramolecular charge transfer (ICT). Using HOMO-LUMO energies, the chemical hardness (η) of the molecules are determined and the chemical stability is discussed. Further, using DFT molecular electrostatic potential (MESP) plots, the electrophilic site and nucleophilic site which are useful in photochemical reactions were identified. The various types of interactions present between the solute-solvent were analyzed by multiple linear regression analysis using Catalan parameters. The preliminary observations and results suggest that, the probe molecules 6MLBH and 6MOBH can be considered as potential candidates for luminescence materials, fluorescent probes and for designing non-linear optical materials in future.

A novel semicarbazone O2N donor ligand, HL, was synthesized by condensation of 2-aminochromone-3-carboxaldehyde with semicarbazide hydrochloride. The HL ligand is allowed to react with several copper(II) salts namely: AcO–, NO3–, SO42– and Cl–, in absence and presence of secondary ligand (SCN-, 8-HQ and 1,10-phen), forming binary and ternary copper complexes. Characterization of the compounds has been done using various techniques like elemental analyses, magnetic moments, conductance measurement, thermogravimetry and FT-IR, UV-Vis, 1H and 13C NMR, EPR and mass spectroscopy. The HL ligand acts as monoanionic O2N tridentate in most complexes, forming Cu(II) complexes with an octahedral and square planar geometrical arrangements. The compounds exhibit luminescence property; promising interesting potential applications as photoactive materials. The ground state (µg) and excited state (µe) dipole moments are estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (Ɛ) and refractive index (n) by using Bilot–Kawski, Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and Reichardt correlation methods. Excited state dipole moment is observed as larger than the ground state dipole moment. The molecular structural parameters of the ligand and its Cu(II)- complexes have been calculated on the basis of DFT level implemented in the Gaussian 09 program at the B3LYP/6-31G(d,p) level and the theoretical data are correlated with the experimental data. The antibacterial properties of the ligand and its complexes have been screened against selected kinds of bacteria and fungi.

Two novel molecules (SCLPY-MeO and SCLPY-CN) are designed based on the N-salycilidene-5-chloroaminopyridine (SCLPY) via introducing the methoxyl (-OCH3) and cyano (-CN) groups at the meta-position of the chlorine atom, respectively, to explore the effect of the substitution of electron-withdrawing and donating groups on the excited-state intramolecular proton transfer (ESIPT) mechanism and photophysical properties of SCLPY, employing the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The significant calculated structural parameters associated with the intramolecular hydrogen bonds (IHBs) have demonstrated that the IHBs intensity is enhanced in the excited state and SCLPY is endowed with the strongest IHB. The partial quenching of the short-wavelength fluorescence in SCLPY-CN has been satisfactorily explained by calculating the transition electric dipole moment and the long-wavelength fluorescence of that exhibits the largest Stokes shifts relative to the other molecules. Moreover, introducing the -OCH3 group has evidently enhanced the luminescent intensity of SCLPY. On account of the potential energy curves (PECs), scanning with gradually elongating the O1-H2 bond, it can be known that the forward proton transfer process is more readily to occur in the S1 state due to the relatively lower energy barriers compared with the ground state. Moreover, SCLPY is provided with the lowest energy barrier, implying that the ESIPT behavior is most likely inclined to proceed in SCLPY. Therefore, it is well illustrated that the introductions of -OCH3 and –CN groups indeed have an impact on the ESIPT process and photophysical properties of SCLPY.

Herein, we have reported the facile synthesis of phase pure and crystalline Eu doped BaTiO3 phosphors via solid-state method. The concentration of the Eu3+ ions in BaTiO3 is varied from 1 to 5 mol%. The structural, morphological and optical properties are characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Visible and photoluminescence (PL) technique, respectively. The structural parameters are further determined by using Rietveld refinement. The excitation spectra revealed that synthesized samples can be excited by near UV (396 nm) and visible blue light (465 nm) and the highest emission intensity is observed at 617 nm under 465 nm excitation, corresponding to the 5D0-7F2 transition of Eu3+ ions. The photoluminescent properties are studied via applying Dexter and Blasse's theory and CIE coordinates are calculated. The decay curves exhibited bi-exponential behaviour for all the samples and lifetimes values varied from 0.409 to 0.320 msec, for 1 to 5 mol% Eu doped BaTiO3 phosphors. The obtained results indicate that synthesized samples have potential applications in optoelectronic and display devices.

In this work, two luminescent iridium complexes were synthesized with 2-phenyl pyridine (ppy) and two phosphine-based ligands. There was large steric hindrance in these phosphine-based ligands, so that there would be enough time for the excited state based on highly luminescent 3MLLCT (metal-to-ligand-ligand-charge-transfer) electronic transformation It was found that there was limited aggregation-induced phosphorescence emission (AIPE) effect in these two iridium complexes since their ligands with large steric hindrance minimized the intermolecular (π-π) interactions between molecules. A distorted octahedral coordination field was found in the single crystals of these two iridium complexes. A systematical comparison on the photophysical parameters of these two iridium complexes in solution state, in solid state and in electrospun fiber was carried out, so that the limited aggregation-caused quenching (ACQ) could be confirmed. The potential surface crossing and energy transfer in the excited state of these two iridium complexes were analyzed by means of density functional theory calculation and temperature-dependent emission spectra. The limited ACQ effect in these two iridium complexes was finally confirmed due to the large ligand steric hindrance, which allowed phosphorescent decay of excited state. High emission quantum yield (0.27) and long emissive lifetime (0.43 μs) in solid state were observed.

The structural changes of 1-(Phenylethynyl)naphthalene (1-PEN) upon excitation from the ground state to the lowest excited singlet state have been assessed from a combined Franck-Condon-Fit of fluorescence emission spectra after excitation of several vibronic bands of 1-PEN and ab initio calculations. An analysis of the infrared spectrum, the laser induced fluorescence (LIF) spectrum and the fluorescence emission spectra is given on the basis of the approximate coupled cluster singles and doubles model (CC2) within the resolution-of-identity approximation and taking spin-component scaling into account. The excited state structure of 1-PEN is found to be planar, with the major geometry changes upon excitation localized in the naphthalene moiety. Electron density shifts from the naphthyl ring to the phenyl ring upon electronic excitation, leading to an increase of the permanent dipole moment of 1-PEN. The lowest electronically excited state of 1-PEN can be labeled as 1 L b -state, with the 1 L a -state energetically quasi-degenerate. The geometry changes, determined from the Franck-Condon analysis are in agreement with this assignment.

The three Schiff base-type Cu(I) complexes [Cu(POP)(N^N)]PF6, N^N = N,N-diphenyl-4-(6-((phenylimino)methyl)pyridin-3-yl)aniline (P1), N-((5-(4-(diphenylamino)phenyl)pyridin-2-yl)methylene)naphthalen-2-amine (P2), N-((5-(4-(diphenylamino)phenyl)pyridin-2-yl)methylene)adamantan-1-amine (P3), were prepared and characterized. The photophysical properties of these Cu(I) complexes is tuned by the addition of different substituents such as phenyl, naphthyl and adamantanyl groups into the backbone of Schiff base ligand. The resulting complexes exhibit high absorption ability in the visible region with molar extinction coefficients of up to 3 7400 M−1 cm−1. The emissions in CH2Cl2 solution are in the range of 551–552 nm with lower quantum yields of 1.1–2.0% and short-lived excited lifetimes of 2.78–3.09 ns for all the complexes at room temperature. The photophysical properties were further explained by DFT and TDDFT methods.

A zinc complex with a N2O2 donor diamine is synthesized and its fluorescence property is explored. The hydrogen bonding environment in its solid state structure is well supported qualitatively and quantitatively with the help of Reduced Density Gradient (RDG) based NCI (non-covalent interactions) index calculation and AIM analyses. Also, the physical nature of other weak non-covalent interactions in the complex is examined. The absorption and emission properties of the complex are explained using density functional theory (DFT) calculations. Analysis of the natural transition orbitals (NTO) shows that the excited state can be mainly characterized by an intra-ligand charge transfer (ILCT) transition within a diamine from the highest-occupied NTO (hole) to the lowest-unoccupied NTO (electron).

Eu(III)-activated Forsterite (Mg2SiO4) nanophosphors have been developed by sol-gel technique at 800 °C. The structural and phase purity of the focused materials have been investigated via X-ray diffraction (XRD) and Fourier transformation infrared (FT-IR) studies. XRD analysis confirms an orthorhombic structure of the prepared phosphors. Transmission electron microscopy (TEM) image depicts somewhat aggregated particles having 50-80 nm size. The peaks at 420 and 464 cm−1, in FT-IR spectrum of Mg2SiO4:Eu3+, have been assigned to MgO6 octahedral. Photoluminescence excitation spectra of nanophosphors specify that these materials can be proficiently excited using UV (393 nm) light and which characteristic fluorescence 5D0 → 7FJ (J = 0 - 3) of Eu3+ ion and strongest one gives red emission peaked at 613 nm (5D0→7F2). Blasse's theory of concentration quenching has been employed to understand the mechanism of energy transfer. The influence of covalent character and structural environment, in the vicinity of trivalent europium ion, on the optical properties has been successfully analyzed using Judd-Ofelt (J-O) analysis The CIE color-coordinates of materials fall into the brighter red region which makes the phosphors effective for optoelectronic applications.

Vertical absorption spectra of selected molecules (pyrimidine nucleobases and 5-azacytosin, 2-amino-1,3,5-triazine, 2,4-diamino-1,3,5-triazine, 2,4,6-triamino-1,3,5-triazine, and s-triazine) were performed using TD-DFT, post-HF, and semiempirical OM2/MNDO methods. From comparing a relatively large set of functionals from the different rungs of Jacob's DFT ladder, the important role of the exact exchange interaction is demonstrated. TD-DFT results with the ωB2GP-PLYP functional (and a few others) are comparable with the post-HF methods. An important finding is also a good accuracy of the semiempirical OM2 approximation, which is used for estimations of lifetimes of the excited states for the same set of molecules. The lifetimes' determination is based on a stochastical treatment of a swarm of MD trajectories. The time-dependent Schrodinger equation is solved for the electronic degrees of freedom while the dynamics of nuclei is treated classically in each trajectory step applying Tully's fewest switch algorithm. The probability of individual states in time is determined and compared with both experimental and computational studies. Our results are in fair accord with available experiments. The nucleobases relatively quickly deactivate – all the relaxation times are below 0.5 ps (in very good accord with measured values). Much longer lifetimes (a few hundred ps) were obtained for other molecules: 5-azacytosin, 2,4-diamino-1,3,5-triazine, and 2,4,6-triamino-1,3,5-triazine. Also, in agreement with experimental data, 2-amino-1,3,5-triazine returns to the ground state on a nanosecond scale.

The molecular, spectroscopic, and excited state properties of synthetic dyes for fiber-based outdoor materials continue to be of commercial interest. Early developments in this area were reported in the 1980s, when the need for dyes for polyester (PET)-based automobile interiors gave rise to commercially viable nitrodiphenylamine yellow, anthraquinone red and blue, and azo red dyes. To augment that initial knowledge base, the present study involved the use of experimental and theoretical methods to help establish the molecular structures and excited state properties of some more recent dyes for producing photostable colors on PET fibers. Having completed the characterization of present-day scarlet, blue, and yellow disperse dyes for PET-based fibers used outdoors, our attention turned to commercially available red and violet dyes. In this regard, HPLC analysis showed that the red product was a mixture containing four components, while the violet product contained only one component. Results from 1H NMR, HRMS, and single crystal X-ray diffraction analyses indicated that the principal components were dyes having a 1-amino-4-hydroxyanthraquinone base structure. The presence of an –OH group alpha to an anthraquinone C=O moiety provides for intramolecular H-bonding and a subsequent opportunity for intramolecular proton transfer in the excited state – as a photostabilizing mechanism. Further, for both dyes, results from the analysis of Frontier HOMO and LUMO isosurfaces indicated strong HOMO-LUMO overlap without molecular gaps and were consistent with strong excited state energy dissipation in a non-destructive way.

The effect of the ring size of the central cavity of a triaza macrocycle on coordination, bonding and properties is described through synthesis, characterization and detailed DFT studies. For this, two new Eu3+ and Tb3+ neutral complexes based on new 12N3 macrocyclic chelator bearing three 8-hydroxyquinoline pendants, [Ln(12N3Me5Ox)(H2O)n].xH2O (Ln = Eu3+ and Tb3+; 12N3Me5Ox = 1,5,9-tris-{(5-methylene-8-hydroxyquinoline)-1,5,9-triazacyclononane} (x = 4 for Eu and x = 5.3 for Tb; n = 2, 3) were synthesized and characterized by elemental analysis, FT-IR, FT-NMR, ESI-mass spectrometry, molar conductance and thermal analysis data. The spectral and analytical data reveal that both the complexes have different coordination number and geometry as compared to its lower homologue. The europium complex is eight coordinate with stoichiometry [Eu(12N3Me5Ox)(H2O)2].4H2O with twist square antiprismatic geometry while [Tb(12N3Me5Ox)(H2O)3].5.3H2O has nine coordination with distorted mono-capped square antiprismatic geometry. The FTIR and TGA analyses confirmed the presence of coordinated waters. The molecular modeling studies suggest that the metal ion can be easily encapsulated in the central cavity of the ligand. The geometries of the complexes are distorted due to parallel π−π and parallel-displaced π−π stacking arrangement between three pendants of 8HQ with inter planner distance are 3.318 and 3.821 A. The 1HNMR spectra of Eu3+ complex spectra were much sharper than that of Tb3+ complex. The photoluminescence spectra showed different behaviour in solid as compared to solution state. In the solid state, and at 77 K, the complexes showed characteristic lanthanide emission in addition to the ligand emission peaks. However, in solution, the lanthanide-centred emissions of the complexes were overlapped with the ligand emissions. A weak antenna effect was observed only in the powder form of the complexes. The vibrational data calculated from the DFT [GGA (B3LY-D3)] optimized structures showed good agreement with the experimental results. The excitation and emission behaviour of the ligand and the complexes were established by molecular orbital analysis of the ground state as well as on the excited state optimized geometry at DFT level. The nature of bonding between the lanthanide ions and the 12N3Me5Ox3−, interpreted by means of the natural bond orbital (NBO) and Morokuma Ziegler energy decomposition analysis (ETS-NOCV) scheme, suggest that the Ln-L bonds are more electrostatic (∼73%) than covalent (∼27%). The covalent character of the complexes increases in the order Tb > Eu. The Slater Condon parameters and spin-orbital coupling constants were calculated from LF-DFT (ligand field density functional theory) calculation. The theoretical Nephelauxetic parameter was also compared with experimental data.

Here we report, experimental and theoretical determination of ground and excited state dipole moments of aryl boronic acid derivatives, 2-Bromophenyl boronic acid (2BPBA) and 2-Isopropylphenyl boronic acid (2IPBA). In both the compounds, Bathochromicshift is observed with increasing solvent polarity indicating π →π* transition due to intermolecular charge transfer interactions. For both the compounds, the ground and excited sate dipole moments are parallel to each other. The excited state dipole moment (μe) is greater than ground state dipole moment (μg) for the compound 2IPBA where as for 2BPBA, excited state dipole moment (μe) is less than ground state dipole moment (μg). Further, experimentally obtained Δμ are compared with those using microscopic empirical solvent polarity ( E T N ). In parallel, the use of Kamlet-Taft parameters to the solvent effect on spectral properties of 2BPBA and 2IPBA are also discussed. The molecular structure, Frontier Molecular Orbitals (FMO), Natural Bond Orbital (NBO) analysis, Non-Linear Optical (NLO) properties of 2BPBA and 2IPBA have been investigated using the (DFT) calculations with B3LYP/6‒311++G (d, p) basis set. The chemical reactivity and kinetic stability of the compounds is shown by differences between the energy levels by analyses of Frontier molecular orbitals. The polarizability and hyperpolarizability computations determine the NLO properties, whereas Natural bond orbital (NBO) analysis showed proton transfer within the selected donor-acceptor depicting large energy of stabilization for the compounds under study.

The potential functions of internal rotation V(φ) (PFIR) of methacryloyl fluoride (MAF) in the ground (S0) and excited (S1) electronic states were reconstructed using the TORSIO program from experimental energy levels of the torsional transitions in the s-trans- and s-cis isomers. The energy levels were obtained from the analysis of the vibrational structure in the high-resolution gas-phase UV spectrum. The (S0) and (S1) equilibrium geometries of the s-trans- and s-cis rotational isomers of MAF as well as structural parameters for a set of points along the relaxed geometry scans, which were used to find expansion coefficients of kinematic function F(φ) in the Fourier series, were calculated using extended multiconfiguration quasi-degenerate perturbation theory, XMCQDPT2/SA(2)-CASSCF(6,5)/aug-cc-pVTZ. The ground (S0) state calculations were also done at the MP2 level of theory. In (S0) state, parameters Vn., barriers of internal rotation ΔH‡ and ΔH of MAF isomers were calculated using two theories. The calculated values of Vn, ΔH‡, ΔH in (S0) state are in good agreement with those derived from the vibrationally resolved UV spectrum of MAF in the gas phase. Within the one-dimensional model, the experimentally derived barrier heights that hinder internal rotation in MAF were found to be 2100 ± 50 cm−1 and 4950 ± 250 cm−1 in the (S0) and (S1) states, respectively. The parameters Vn and ΔH‡ in (S1) state are determined for first time.

In this effort, the correlation between polymer immobilization effect and excited state of emitting copper complex was discussed. An electron-pulling diamine ligand having an oxadiazole ring and a fluorine atom was synthesized. Its corresponding Cu(I) complex was synthesized with a phosphorous ligand (PPh3) having obvious steric hindrance as auxiliary ligand. Its geometric structure, electronic transition and photophysical parameters were discussed in detail. A distorted tetrahedral coordination field was adopted by this Cu(I) complex. Its onset electronic transition was confirmed as a charge transfer one and suffered from structural relaxation badly. Using electrospinning method, this Cu(I) complex was dispersed and immobilized into a polymer host so that structural relaxation of its excited state could be limited. A systematical comparison between various states of this complex, in solution, in solid state and in fibrous samples, was performed. It was finally confirmed that this polymer matrix served as a promising supporting host, offering a rigid and protective microenvironment for dopant molecules which effectively limited their MLCT structural relaxation and improved their photostability.

The study on the fluorescence and UV–Vis absorption of some iminocoumarins at ambient temperature in several solvents showed a bathochromic shift with the increase of the solvent polarity. The use of the solvathochromic method allowed us to determine the dipole moment in both ground and excited states. The studied molecules exhibit much higher dipole moments in the excited state than in the ground state, which can be due to the redistribution of π-electron densities in the excited state making molecules more polar with higher dipole moments. Furthermore, HOMO–LUMO gap were also estimated theoretically using B3LYP/6–311 + G (d,p) level of theory; the low energy gap indicated the eventual charge transfer interaction occurring in the molecules, and responsible for their light emitting properties.

Synthetic dyes having high photostability on hydrophobic fibers such as poly(ethylene terephthalate) (PET) are of interest for use on textile substrates for outdoor applications. While much is known about photostable dyes developed for PET in the 1980s, owing to their viability for use in automobile interiors, little has been published on currently viable photostable disperse dyes. As part of an effort to help fill this void and to facilitate future photostable disperse dye design, the present study involved the use of experimental measurements and modelling studies to help characterize the molecular structures of commercially viable dyes for producing photostable colors on PET fibers, beginning with a pair of blue dyes. With the aid of HR-MS, 500 MHz 1H NMR, and X-ray crystallography, it was established that the two dyes are structural isomers having 1,5-(OH)2-anthraquinone (AQ) and 1,8-(OH)2-AQ base structures. It is proposed that the photostability of these dyes arises from the presence of multiple OH/NH groups ortho to the AQ C O groups which enables them to dissipate excited state energy through intramolecular proton transfer. Further, using DFT-based molecular modelling studies, it was shown that the dye having the 1,5-(OH)2-AQ base structure has a lower ESOP than the isomeric dye having the 1,8-(OH)2-AQ base structure. Similarly, results from calculating Frontier HOMO and LUMO isosurfaces indicated that the LUMO lobes of the latter dye are larger, suggesting that this dye undergoes excitation faster than the 1,5-(OH)2-AQ isomer.

Steady state and time resolved spectral properties of 7,8-benzoquinoline (7,8-BQ) have been reinvestigated in a series of organic solvents of different proticity, polarity and wide range of pH. The salient features of this work are the effect of hydrogen bonding in protonation reaction which is explored through its behaviour in water and strong hydrogen bond donating solvent (trifluoroethanol). Quantum yield and rates (radiative, non-radiative and excited state protonation) have been calculated and discussed. Irreversible diffusion controlled excited state proton transfer in water and faster excited state protonation in trifluoroethanol is observed.

A trio of 1,4-diaryl-1,3-butadiynes with methoxy and trifluoromethoxy substituents in the 4- and 4′-positions were prepared in useful yields (42% for one, 95+% for the others), their structures determined and their purity ascertained. Analysis of the single crystal X-ray data for the three compounds revealed that two were mostly planar with small dihedral angles of 6–9° between their aryl rings, while one existed in a twisted conformation with a dihedral angle of approximately 53° between it's aryl rings. The solid-state absorption spectra of all three compounds were similar, with structured absorptions at approximately 340 nm. One of the compounds had absorption bands at 263 and 457 nm. Two of the compounds had similar emission bands with maxima that ranged from 440 to 450 nm, while the other was quite different, with a broad emission band with a maximum at 564 nm. Each of the three compounds had excited state decay traces that were fit to tri-exponential curves which yielded three lifetimes: a longer one attributed to aggregate emission, a shorter one arising from an intermolecular charge transfer transition, and a medium one that is assigned to a locally excited transition.

The spectroscopic behavior of benzylidene malonitrile (BZM), a donor-π-conjugate-electron acceptor compound, is reported in various solvents. Kamlet–Taft and Catalan models were used to evaluate specific and non-specific solute-solvent interactions. Solvent polarizability (SP) was found to be the dominant factor affecting the absorption and fluorescence spectral shifts. The π →π* transitions was assigned between HOMO and LUMO, based on time-dependent density functional theoretical calculations. The dipole moment of BZM in the ground and excited states were calculated using Stokes shift and solvent polarity functions. The experimental ground state dipole moment (μg = 1.7 D) was found to be lower than that in the excited state (μe = 5.5 D). In binary solvent mixtures, BZM showed both ideal (DMSO/ethanol) and non-ideal (DMSO/acetone and DMSO/dioxane) behaviors. The formation constants in DMSO/ethanol was much lower as compared to the other two mixtures. BZM also exhibited self-quenching fluorescence which is attributed to the primary inner filter effect.

Single crystals of an organic charge-transfer compound, 4-nitrobenzyl isoquinolinium picrate, [4NO2BzIQl][PIC](1), were grown by slow evaporation technique at room temperature. Single crystal XRD and powder XRD studies conform the crystal structure and crystalline nature. In the title compound, the [4NO2BzIQl]+ cations and the [PIC]- anions stack into a columnar structure through π···π and C H···π interactions. The FT-IR and Raman spectra were recorded and analyzed with the aid of density functional theory calculations in order to make a suitable assignment of the observed bands. The simulated spectrum satisfactorily coincides with the experimental UV–visible spectrum. Thermal stability and the major gaseous products of decomposition at 293 °C were examined by TG-DTA-MS technique. The material shows three main emission peaks about 385, 467 and 538 nm upon excitation at 241 nm in solid state at room temperature. The excited state energy from theoretical UV–vis spectra, the total energy of intramolecular interactions and nonlinear optical properties were studied using DFT calculations.

Solvatochromic behaviour of two 3-(2-hydroxybenzoyl) coumarins 3 and 4 has been studied in different solvents at room temperature. Both derivatives show emission at 371 nm and 422 nm with large Stokes shift of 45 and 74 nm, respectively. Higher values of dipole moment have been observed for excited state compared to the corresponding ground state values, indicating an intramolecular charge-transfer (ICT). The electronic structural and spectroscopic properties of 3 and 4 in gas and in different solvents were calculated by the conductor-like polarizable continuum model (CPCM) and have been investigated by DFT/TD-DFT calculations to account for solute-solvent interaction. Excitation energies and oscillator strengths were calculated and HOMO-LUMO levels have been investigated in gas and solvent phases. The comparison of the atomic charge distributions in the ground and excited states of both 3a and 4a rotamers implies also the intramolecular charge transfer (ICT) process during the excitation period.

In this contribution, we report the synthesis of benzofuranyl-derived flavylium salts whose structure have been confirmed by mass spectrometry and by NMR. Their structural and electronic properties have been studied by absorption and fluorescence spectroscopies and DFT calculations. Theoretical structural parameters of the calculated compounds were validated by the experimentally obtained X-Ray structure of 2-(2-benzofuranyl)-7-hydroxy-1-benzopyrylium perchlorate. The absorption spectra of the benzofuranyl-derived flavylium salts were simulated with good accuracy with respect to the experimental data. In equilibrated buffered solutions, the pH-driven multi-state evolution reaction of novel benzofuranyl-flavyliums afforded trans-chalcone and chalconate derivatives as the predominant species. The elusive nature of the species formed in solution was corroborated by chemical quantum calculations. The fluorescence bands of the flavylium, trans-chalcone and chalconate forms were assigned to their fluorophoric units by selective excitation of each one of the species present in solution. Fluorescence spectroscopy strongly suggests that 2-(2-benzofuranyl)-7-hydroxy-1-benzopyrylium perchlorate displays excited state proton transfer (ESPT).

N-phenyl-3-para nitro phenyl isoxazolidine-5-carbonitrile compound (C16H13N3O3) has been synthesized and characterized by single-crystal X-ray diffraction at 293 K. The title compound crystallized in the orthorhombic system (Pbca space group) with Z = 8 and the following unit cell dimensions: a = 12.9970 (9) A, b = 7.3090 (9) A, c = 29.658 (2) A. Raman spectroscopy has been investigated at room temperature. Raman spectra have been measured at 647.5 nm excited laser lines in the frequency range 125–4000 cm−1. The Raman spectrum is characterized by a series of bands in the 150–3500 cm−1 spectral range. The structure of the this compound was optimized by density functional theory (DFT) using B3LYP method and shows that the calculated values obtained by B3LYP/6-31G(d,p) basis are in much better agreement with the experimental data than those obtained by B3LYP/6- 31G(d). The vibrational frequencies were evaluated using density functional theory (DFT) with the standard B3LYP/6-31G(d,p) basis. The Molecular Frontiers Orbitals (FMOS) calculation is carried out to determine the charge transfer within the molecule.

Vacuum ultraviolet photoabsorption spectra of pentane (C5H12) structural isomers (n-pentane and isopentane) are recorded in the 6–11.5 eV region using a synchrotron light source. The photoabsorption spectra for both the pentane isomers showed a continuum, beginning at about 7.5 eV and increasing in intensity up to 10.5 eV with few broad peaks devoid of discernible structures. Quantum chemical calculations using the DFT methodology predicted the optimized ground geometry and fundamental frequencies for neutral and cationic pentane isomers. The excited electronic state vertical energies are computed using time-dependent DFT and allied to construe the experimental spectra. From theory, the electronic spectra of pentane isomers encompass mostly valence-Rydberg mixed type transitions, converging to the first four ionization potentials while isopentane at 9.62 eV predicted a uni-molecular dissociation to C2H5• and C3H7• radicals. The plot of potential energy curves for the first few excited states facilitated understanding the spectral features UV region and its photodissociation mechanism for both pentanes. The broad continuum spectra in both isomers may be attributed to strong valence - Rydberg interactions along with a contribution from the presence of conformers, low torsional modes and Rydberg series converging to close-lying ionization potentials. Gas phase infrared spectra of pentane isomers in the 500–4000 cm−1 region were revisited and DFT calculations clarified few vibrational assignments. The present study provides a comprehensive understanding of the absorption spectra in the VUV and IR regions of n-pentane and isopentane.

Pyrene and its OH, NH2, and CN substituted derivatives were investigated experimentally by using UV/Vis absorption spectroscopy, steady state and time-resolved fluorescence spectroscopy in different polarity solvents. The computational part includes investigation of Pyrene and derivatives in excited S1 state in gas phase and in solution. Calculations were carried out with density functional theory (DFT) and time-dependent density functional theory (TDDFT) at B3LYP/6-311++G(d,p) level. Both ground and excited state geometries were fully optimized in gas phase and in solution. Solution calculations were carried out with Polarizable Continuum Model (PCM). Current results indicate that solvent polarity did not affect Py and its derivatives except PyNH2. Solvent has minor effects on PyCN and PyOH. Although PyNH2 has he smallest HOMO-LUMO energy gap, it is not the best candidate due to its shortest fluorescence lifetime. On the other hand, PyOH and PyCN have longer lifetimes. Therefore, it is concluded that investigated molecules are appropriate candidates for photosensitive applications in the order of PyNH2

Understanding electronic structures and excitation properties is a fundamental issue to develop novel electron donor (D) and acceptor (A) molecular dyad that can be applied in optoelectronic systems. Here, the geometry, electronic structures, and excitation properties of three meso-pentafluorophenyl substituted zinc porphyrin fullerene ((F15P)ZnP C60) dyad were analyzed based on density functional theory (DFT) and time dependent DFT (TDDFT) calculations. The geometrical parameters provide the D-A distance is about 18.19 A. The electronic structure analysis indicates that the highest occupied molecular orbital and the lowest unoccupied molecular orbital are localized in porphyrin core and C60, respectively. The transition configurations and the MOs suggest the excited states at the absorption maxima are local excited states, while the charge transfer (CT) states are transient intermediates. The population analysis supports the first singlet/triplet excited states are local excitations in porphyrin (LEP). Quasi-degeneracy of excited states between LEP and local excitation in C60 (LEC) enable the partial delocalization of eigenstates and excitation-energies over the D and A in dyad, while the quasi-degeneracy between CT and LEP generate synergistic enhancement effects for CT. The results of this work could be helpful to understand optoelectronic properties of (F15P)ZnP C60 dyad.

The effect of different substituents on the excited state intramolecular proton transfer (ESIPT) of 1-aryl-2-(furan-2-yl)butane-1,3-diones (AYFBD), namely OFBD, TFBD, MFBD and FFBD are studied by employing the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. By comparing the geometric configurations and infrared vibrational spectra of the first excited state (S1) with those of the ground state (S0), it can be concluded that the intramolecular hydrogen bonds are strengthened in S1 state. The calculated peaks of absorption and fluorescence spectra of AYFBD derivatives in keto form are consistent with experimental results reported previously (Journal of Organic Chemistry, 2017, 82, 12097). We can also confirm that the intensities of the intramolecular hydrogen bonds in the S1 state are enhanced by analyzing the frontier molecular orbitals and the infrared spectra. To further investigate the ESIPT mechanism of AYFBD derivatives, the potential energy curves (PECs) of S0 and S1 states are scanned by varying O1 H2 distance, which demonstrates that ESIPT occurs in the S1 state of all the AYFBD derivatives and follows the order: FFBD > MFBD > TFBD > OFBD.

A new Dy3+ activated Ba7(BO3)3(SiO4)Cl phosphor with complex anionic groups was synthesized by the high temperature solid state reaction technique. The X-ray powder diffraction analysis showed that the phosphors crystallized in polar space group P63mc of the hexagonal system. The excitation and emission spectra, decay curves and chromaticity coordinates were characterized to investigate the photoluminescence properties. The Ba7(BO3)3(SiO4)Cl:Dy3+ phosphors could be effectively excited by UV–visible light from 280 to 500 nm. The emission spectra exhibited three emission bands peaking at 480 (blue light), 576 (yellow light) and 665 nm (red light), which were due to the 4F9/2-6H15/2, 4F9/2-6H13/2 and 4F9/2-6H11/2 transitions of Dy3+, respectively. When Dy3+ concentration exceeded 12 mol%, the concentration quenching occurred. The critical distance between Dy3+ ions was calculated to be about 9.22 A. In addition, the chromaticity coordinates of the phosphor are (0.33, 0.37), and the point is in the white region.

Since acenaphthene isolated in an Ar matrix at 15 K emits green-yellow phosphorescence for ∼10 s after stopping UV-light irradiation, its transient IR spectrum is expected to be measured with an FTIR spectrometer during UV irradiation. The transient spectrum observed is found to be consistent with the simulated spectrum of acenaphthene in the lowest electronically excited triplet (T1) state calculated at the B3LYP/6–31++G(d,p) level. The spectral pattern obtained using the B3LYP functional, which is the most popular DFT hybrid functional, reproduces the observed spectrum more satisfactorily than that obtained using the recently proposed M06-2x functional, although the optimized geometrical parameters in the both calculations are not so different from each other. The IR-band assignments of the T1 state and the structural changes from the S0 state to the T1 state are discussed based on the results of B3LYP calculation.

The radiationless decay of the isothiazole and thiazole molecules in the gas phase is investigated by a combination of static MS-CASPT2 computations with dynamics simulations, and some deactivation pathways are identified leading from the lowest excited singlet (S1) state back to the electronic ground (S0) state. The dominant relaxation pathway of the excited isothiazole is found to involve out-of-plane ring deformation (ring puckering) at the C4=C5(H8) S1 moiety, while the excited-state decay of thiazole can proceed through the ring puckering and S1 C2 bond cleavage pathways both of which happen at the S1 C2(H6) = N3 moiety. On the basis of the calculation results, we suggest that both ring-puckering and ring-opening routes should play rather important roles in the photophysics and photochemistry of heterocyclic molecules, and the position of the N atom in the heterocyclic ring has an effect on the excited state deactivation.

In the present study Ca2P2O7:Ce3+ pyrophosphate phosphor was synthesized by modified solid state diffusion. Materialization of crystalline phases were recognized by X ray diffraction pattern and their photoluminescence properties were studied using excitation and emission spectra under ultraviolet ray excitation ranging from 250 to 400 nm. The Ca2P2O7:Ce3+ phosphor was excited at 298 nm, the emission spectrum exhibited two intense bands at 362 nm and 390 nm emission due to 5d → 4f transitions of Ce3+ ions. The morphological investigations of Ca2P2O7 pyrophosphate have been carried out by scanning electron microscopy and fourier transform infrared spectra at room temperature was also examined. Stoke's shift, type of interaction between activator and the influences of the doping concentration of Ce3+ on the luminescence characteristics are discussed from photoluminescence excitation and emission spectra.

Two organic salts compounds C8H13Cl2N5O(1) and C8H13Br2N5O(2) were prepared by slow evaporation at room temperature and characterized through single-crystal X-ray diffraction, photoluminescence, IR and UV–Vis diffuse reflectance spectroscopy (UV/DRS) from which the optical properties were determined. The asymmetric unit of (1) and (2) consists of a discrete guanidinobenzimidazolium, two halide anions X− (X = Cl, Br) and one crystallization water molecule. The crystal structures of the two title salts are stabilized by N H … X, O H … X, N H⋯O and C H … X hydrogen bonds. Moreover, the protonated 2-guanidobenzimidazole shows a π-π interaction adding extra stability to the three-dimensional architecture. The ground state geometries of the two compounds were optimized using density functional theory (DFT) at the 6-311+G(2d, 2p) level of theory. In order to study the excited states, time-depending density functional theory calculations were performed on the optimized structures at the same level of theory. The calculated electronic absorption and infrared spectra were in good agreement with the experimental ones.

Density functional theory (DFT) calculations were performed to examine the excited triplet states of various eight iridium(III) complexes and the relationship between these states and the emission spectra. The complexes investigated were 1 [Ir(NO3)2(phen)2]PF6, 2 [IrCl2(phen)2]PF6, 3 [Ir(NO2)2(dmbpy)2]PF6, 4 [IrCl2(dmbpy)2]PF6, 5 [IrCl2(tmphen)2]PF6, 6 [IrCl2(bqn)(dmbpy)]PF6, 7 [IrCl2(bqn)2]PF6 and 8 [IrCl2(bqn)(phen)]PF6. Here, phen is 1,10-phenanthroline, dmbpy is 4,4’-dimethyl-2,2’-bipyridine, tmphen is 3,4,6,7-tetramethyl-1,10-phenanthroline and bqn is 2,2’-biquinoline. Complexes 1, 3, 5, 6 and 8 were newly synthesized for this study and exhibited pronounced phosphorescent emission for 5, 6 and 8. All complexes were calculated to possess excited triplet states. The excited states of the complexes are primarily associated with metal-to-ligand charge transfer (MLCT) and π-π* transitions.

LnIII coordination compounds were synthesized with two benzimidazolic ligands, 2 pb = 2-(2-pyridyl)benzimidazole and 4tb = 2-(4-thiazolyl)benzimidazole, with Eu, Gd, Tb and Dy, namely: [Ln (NO3)3 (Ln)2]⋅S, where Ln = 2 pb, 4tb and S = solvent. They were characterized by IR, 1D and 2D 1H and 13C NMR, solid state UV–Vis–NIR absorption and emission and EPR spectroscopies, X-ray powder diffraction, elemental analyses, electrical conductivity and magnetic susceptibility. The compounds of EuIII with 2 pb and 4tb, TbIII and DyIII with 4tb showed luminescence at RT in the solid state; their emission life time ranged from 0.026 to 1.82 ms. 2 pb and 4tb sensitized lanthanides luminescence. Results of DFT theoretical calculations for the ligand (H2L) are used to assign the ligand singlet and triplet excited state energy levels. Additionally, a full analysis of the X-band EPR spectra in the solid state gave the following results, at 297 K for [Gd(NO3)3 (2 pb)2]·CH3COCH3, g = 1.990, |D| = 0.0687 cm−1, E = 0.0165 cm−1 and λ = |E/D| = 0.240; for [Gd(NO3)3 (4tb)2]⋅CH3COCH3, g = 2.000; |D| = 0.0670 cm−1, E = 0.000 cm−1 and λ = |E/D| = 0.000. At lower temperature, 128 K, compounds showed an increase of the rhombicity as the temperature decreased.

This work was part of an investigation aimed at characterizing the molecular and excited state properties of currently available disperse dyes developed to provide stability to extensive sunlight exposures when adsorbed on poly(ethylene terephthalate) (PET) fibers. Having completed the characterization of yellow, magenta, and cyan disperse dyes for PET-based fabrics used outdoors, our attention turned to the colors designed to enhance the color gamut of a standard 4-member (cyan/yellow/magenta/black) color set. The present study pertained specifically to the characterization of commercially available scarlet dyes. In this regard, HPLC analysis showed that a scarlet product used for PET coloration was mainly a 70/30 mixture of dyes, and the use of HRMS and single crystal X-ray diffraction analyses indicated that these two dyes were azo compounds derived from isomeric pyridine-based couplers which differed in the location of the primary amino ( NH2) and anilino ( NHPh) groups attached to the pyridine ring. One dye structure has the NHPh group para to the azo group (Sc2), while the other has that group in the ortho position (Sc3). The presence of either ortho substituent provides photostabilization through intramolecular H-bonding with the azo moiety. Further, results from molecular modeling studies showed that the lower excited state oxidation potential of Sc3 relative to that of Sc2 allows Sc3 to function as an energy quencher for the excited state of Sc2 – through thermodynamically favorable electron transfer.

In this research, we report the results of experimental and density functional theory (DFT)/time-dependent DFT analyses of two new azo derivatives that absorb light in the visible range: (E)-2-((4-(diethylamino)phenyl)diazenyl)-6-methoxy-3-methylbenzo[d]thiazol-3-ium (I) and N,N-diethyl-4-((6-methoxybenzo[d]thiazol-2-yl)diazenyl)aniline (II) in the presence of water (I) and chloroform (II). The molecular geometry and excited states of the compounds were investigated, and their natural bond orbital, frontier molecular orbital, quantum theory of atoms in molecules, and nonlinear optical (NLO) parameters were calculated. In addition, Fourier-transform infrared, nuclear magnetic resonance, and ultraviolet/visible spectral parameters were generated from the derived structures and compared to experimental spectral parameters. The practical applicability of the azo derivatives was investigated by determining their electronic and NLO properties, which demonstrated that both molecules have potential for optoelectronic and photonic applications. A high degree of approximation between the calculated and experimental results was demonstrated.

The intriguing intrinsic photoluminescence (PL) properties of gold nanorods (AuNRs) have been intensively studied over the last years, not only in the linear but also in the non-linear optics regime, boosting their applicability in various fields of nanobiotechnology. In the present work, we investigate the two-photon excited (TPE) intrinsic PL of different-aspect ratio (AR) synthesized AuNRs, coated with gelatin (g@AuNRs), by performing innovative fluorescence spectroscopy - fluorescence lifetime imaging microscopy (FLIM) combined studies on individual g@AuNRs. In the first step, we employ Finite-difference time-domain (FDTD) simulations to confirm the optical response of AuNRs before and after coating with gelatin. While TPE FLIM assays performed under 800 nm excitation expose some interesting aspect regarding the AR-dependent TPE PL emission generated by individual g@AuNRs, spectroscopic measurements reveal that the TPE PL has a lifetime of around 100 ps and overlaps the corresponding transverse plasmonic band. Finally, we evaluate the effect of laser excitation power and wavelength on the TPE PL, pointing towards the important correlation between these parameters and the TPE PL performance of g@AuNR, as possible contrast agents for label-free TPE fluorescence imaging applications.