Solvatochromic Correlations Research Articles

Effect of Ag2O nanoparticles on the excited state dipole moment of a novel BMNFC molecules through solvatochromic shift method

We experimentally determined the ground and excited state dipole moments of BMNFC (5-bromo-N’-[(Z)-(4-methoxyphenyl)methylidene]naptho[2,1-b]furan-2-carbohydrazide) dye using the solvatochromic shift method and various solvatochromic correlations, including Lippert’s, Bakhshiev’s, Kawski-Chamma-Viallet’s, and solvent polarity equations. We employed the B3LYP/6-311G (d) level of theory to calculate the HOMO, LUMO, and MESP. In this study, we synthesized Ag2O nanoparticles using a quick and cost-effective chemical reduction method. Then, we used carboxymethylcellulose (CMC) as a capping agent. We studied the size, shape, and composition of these nanoparticles using a variety of analytical techniques. Transmission electron microscopy (TEM) analysis revealed a spherical morphology with an average diameter of 17 nm. The results show that adding Ag2O nanoparticles to BMNFC molecules changes their symmetric charge distribution, which in turn enhances their dipole moment. Molecules of enhanced dipole moment have attractive features in biomedical applications. Each molecule’s symmetry point group determines the extent to which nanoparticles affect the BMNFC molecule.

Systematic photophysical investigation on pyrromethene 650 laser dye: Experimental and DFT approach

In the current study, we have chosen a highly fluorescent laser dye called pyrromethene 650 (PM-650) to investigate its photophysical properties using theoretical and experimental methods. We measured the absorption and emission spectra of PM-650 in polar protic and polar aprotic solvents at ambient temperature. Bathochromic and hypsochromic shifts were observed in the absorption and fluorescence spectra of the laser dye, confirming the presence of transitions between π → π* and n → π* states. We further estimated the ground and excited state dipole moments of PM-650 through experimental (solvatochromic correlations) and theoretical (ab initio) techniques, and compared the results. Interestingly, the PM-650 displayed an increased excited state dipole moment when contrasted with its ground state. Furthermore, using the B3LYP/6-311G++(d, p) approach, we estimated the natural bond orbital and molecular electrostatic potential map of PM-650 and discussed the results. Additionally, we theoretically determined the HOMO-LUMO energy band gap of PM-650 in different solvents with varying polarities, and found good agreement with the experimentally obtained values. To assess the reactivity and softness of PM-650, we calculated global chemical reactive descriptor values based on the theoretically estimated HOMO-LUMO. Our results suggest that PM-650 is highly reactive and possesses a soft nature.

Systematic Photophysical Interaction Studies Between Newly Synthesised Oxazole Derivatives and Silver Nanoparticles: Experimental and DFT Approach.

In this study, the photophysical properties of oxazole derivatives such as 5-(furan-2-yl) -4-tosyloxazole (OX-1) and 5-(2-bromothiazol-4-yl)-4-tosyloxazoles (OX-2) were investigated using theoretical and experimental techniques. The ground and excited state dipole moments were empirically obtained utilising the solvatochromic shift technique and several solvatochromic correlations such as Lippert's, Bakhshiev's, KawskiChamma- Viallet's, and solvent polarity equations. The ground state dipole moments, HOMO-LUMO and molecule electrostatic potential map were also computed using ab initio calculations and evaluated using Gaussian 09 W software. Furthermore, spectroscopic interactions between newly synthesised dyes (OX-1 and OX-2) and freshly synthesised silver nanoparticles (size 40nm) were studied. Increased absorbance and widening of absorption spectra for both dyes in the presence of varied quantities of silver nanoparticles show the potential of dye-nanoparticle interactions. Fluorescence quenching has been detected for both dyes in the presence of colloidal silver nanoparticles, indicating dynamic quenching, and a significant overlap between the absorption and emission spectra of the silver nanoparticle reveals that fluorescence quenching is also due to energy transfer.

Solute-solvent interactions, electrostatic & covalent surface analysis, and pharmacokinetic studies via in-silico simulation on diethyl 3-hydroxyglutarate: Anti-hypercholesterolemia activity

In this study, theoretical investigations of the anti-hypercholesterolemia molecule diethyl 3-hydroxyglutarate (D3HG) have been carried out using DFT techniques. Vibrational spectral analyses were utilized for the structural determination after the compound's stability was identified through DFT optimization. As per the QTAIM findings, the highest electron density and electron distribution asymmetry were found at O4C9 and O510 in the molecule D3HG. Under the topological evaluation, the covalent and electrostatic interactions were assessed by Laplacian electron density (∇2ρ(r)) and reduced density gradient (RDG). Studies of solvent effects on electronic absorptions, molecular electrostatic potentials, global reactive descriptors, and Fukui functions have been analysed to understand better the mechanism causing chemical responsiveness. First-order hyperpolarizability (β) and natural bond orbital (NBO) stability calculations were also included. Solvatochromic correlations are used to approximate the referred molecule's reactions to polar and non-polar solutions as well as the solute-solvent interactions. Using Lipinski's rule, the molecule's drug-likeness study was carried out; pharmacokinetics and the D3HG molecule's interactions with iso-enzymes were also explored. A molecular docking study also demonstrates the efficacy of the title molecule to have anti-hypercholesterolemia activity.

Synthesis of Naphtho-[2,3]-furan derivatives for investigative insights into solvatochromic behaviour

The paper delineates the synthesis of naphtho-[2,3]-furan derivatives (viz. a viz. naphtho-[2,3]-furan-3-yl acetate (NF), 9-nitronaphtho-[2,3]-furan-3-yl acetate (NNF) and 9-bromonaphtho-[2,3-]-furan-3-yl acetate (BNF)) using a multistep approach. The products were obtained in high yields and characterized by FT-IR, 1H NMR, 13C NMR, and HRMS spectroscopy. The absorption and fluorescence spectra of these derivatives were recorded in the solvent of different polarities. Solvatochromic correlations were employed to estimate ground state (μg) and excited state (μe) dipole moments. The results suggested higher stability of molecules in the singlet excited state than in the ground state. Theoretical investigations indicated that the ΔEHUMO-LUMO gap varied as ΔENF>ΔEBNF >ΔENNF. The thermogravimetric analysis (TGA) confirmed the higher stability of NNF as compared to BNF and NF.

Theoretical and photophysical investigation of biologically active fluorophore: 2-amino-6-chlorofluoren-9-one

The optimized geometric parameters of the 2-Amino-6-chlorofluoren-9-one (2A6CF9O) compound were estimated by employing density functional theory. The electronic characteristics of the molecule were explored using molecular frontier orbital energies and the MEP surface. Kamlet's and Catalan's multiple linear regression techniques along with different polarity functions were used to investigate the influence of pure solvents on spectral properties. In the system, both general solute-solvent and hydrogen bonding interactions are active. However, as compared to normal solute-solvent interactions, hydrogen bonding interactions have a smaller role. In addition, using computed ground state dipole moment, solvatochromic correlations were employed to infer excited state dipole moment.

Synthesis, spectroscopic properties, and DFT correlative studies of 3,3′- carbonyl biscoumarin derivatives

• Photophysical properties of probes Bis-Coumarin derivatives have been investigated. • The probes are more polar in the excited state than the ground state. • HOMO-LUMO & Optical energy band gaps are in agreement with each other. • Chemical hardness studies suggest soft nature for the probes. • MESP plots exhibit both electrophilic & nucleophilic sites. A facile and simple method for the synthesis of a library of 3,3′- Carbonyl biscoumarin derivatives via a one-pot chemical reaction is reported. The synthesized fluorescent dyes were purified and characterized by analytical methods. The IR, 1 H-NMR, and MS results confirmed the corresponding structure of the fluorescent dyes. The absorption and fluorescence spectra of fluorescent dyes were recorded in different solvents of varying polarity to understand the solvatochromic behaviour and dipole moments. Stoke's shift exhibits a redshift with an increase in solvent polarity for all molecules indicating a π→π ∗ transition. The ground state dipole moments of all fluorescent dyes are estimated theoretically from ab initio computations (integral equation formalism of polarizable continuum model) and experimentally from the solvatochromic method and the results are compared. Further, using solvatochromic correlations like Lippert's, Bakhshiev's, Kawski-Chamma-Viallet's, and solvent polarity parameter the excited state dipole moments are determined. Results show that the excited state dipole moments are higher than the ground state dipole moments which suggests that, all fluorescent dyes are more polar in the excited state. The HOMO-LUMO energy gaps computed from density functional theory and absorption threshold wavelengths are found to be in good agreement and also support intramolecular charge transfer (ICT). Using HOMO-LUMO energies, the chemical hardness (η) of the molecules is 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 preliminary observations and results suggest that the fluorescent dyes can be considered as potential candidates for fluorescent probes and construction of dye-sensitized solar cell in future

Solvation, rotational dynamics, photophysical properties study of aromatic asymmetric di-ketones: An experimental and theoretical approach

In this article we have investigated the solvation, rotational dynamics and photo physics of diketone derivatives DK-2 and DK-3 in alcohols and alkanes at room temperature through both a time-resolved fluorescence depolarization technique and steady state. Viscosity of dissolvable varies linearly with respect to rotational times of the molecule. Outcomes are investigated by utilizing the theory of hydrodynamic (SED) Stokes- Einstein-Debye to evaluate the friction with stick and slip limiting conditions. In addition, using the solvatochromic shift and quantum chemical technique aromatic di-ketone derivatives, 1-(4′-dodecyl-[1,1′-biphenyl]-4-yl)-3-(4-ethoxyphenyl) propane-1,3-dione (DK-2) and 1-(4′-dodecyl-[1,1′-biphenyl]-4-yl)-3-(4-(nonyloxy)phenyl)propane-1,3-dione (DK-3) estimated properties of fluorescence. The excitation and emission spectra of DK-2 and DK-3 have been observed in several solvents. The dipole moments calculated using DFT theory and solvatochromic correlations. Estimated (μg) value by DFT theory is relatively greater than the solvatochromic shift techniques. The dipole moments of excited state (μe) are found to be more prominent than dipole moment of ground states (μg) which approves π → π* transition. The variance of dipole moments (Δμ) was determined from microscopic solvent polarity parameter (ETN) and solvatochromic shift technique and outcomes are compared.

Solvatochromic correlation analysis of monomolecular SN1/E1 heterolysis reactions of tertiary haloalkanes

A solvatochromic analysis of the reaction of the solvent-dependent heterolysis reaction of tertiary haloalkanes, based on the properties of the solvents used, allows visualizing and interpreting the intermolecular solute/solvent interactions that control these important chemical processes.The results achieved confirm that the rate of these chemical processes increases in a balanced way with an increase in the polarizability, the dipolarity, and the hydrogen-bond donor (HBD) acidity of the solvents, and to a much lesser extent with their their hydrogen-bond acceptor (HBA) basicity. Contrary to what is currently accepted, namely that the rate of these processes is not or is negatively affected by the solvent's HBA basicity (nucleophilicity), we conclude that if it does, it is positively affected. We also conclude that the Gibbs activation energy of the heterolysis of 2-chloro-2-methylpropane (t-BuCl) decreases by the four solvatochromic contributions to the overall intermolecular solute/solvent interactions.

Optical, photo physical parameters and photo stability of 6-Substituted-1, 2, 4-Triazine mono glucosyl derivative to act as a laser dye in various solvents.

The optical properties of a visible absorption range6-Substituted-1, 2, 4-Triazine mono glucosyl fluorescent derivative dye, such as absorption spectra, emission spectra in different solvents, were experimentally investigated. As well, some important photo physical parameters such as extinction coefficient (ε), cross-sections of the absorption (σa) and the emission (σe), quantum yield (фf), fluorescence lifetime, oscillator strength (f), the dipole moment (μ), decay rate radiative constant (kr), energy yield of fluorescence (Ef) and the length of attenuation Λ (λ) were assessed. The ground-state (μg) and excited-state (μe) dipole moments by solvatochromic correlations method were reported. The dye amplified spontaneous emission (ASE) of 2×10-4M with different input pumping energies of a continuous wave blue diode laser (λ=450nm) was studied. Photostability of dye was observed that was decreased to 53% of its initial energy by pumping with 100mW of diode laser after exposure to 120min.

Fluorescence properties of aromatic asymmetric di-ketone compound in polar and non-polar solvents

Using the quantum chemical and solvatochromic shift technique aromatic unsymmetric di-ketone compound1-(4’-dodecyl-[1,1’-biphenyl]-4-yl)-3-(3,4,5-trimethoxyphenyl)propane-1,3-dione (DK1) fluorescence properties were estimated. The excitation and emission band of recently synthesized DK1 have been examined in various dissolvable. The dipole moments evaluated utilizing Gaussian software and Solvatochromic correlations. Evaluated (μg ) value by Gaussian method is comparatively larger than the solvatochromic shift methods. It is seen that the energized state dipole moments (μe ) are more prominent than the ground state dipole moment (μg ) which authorizes π → π* transition. The (Δμ) were also estimated both from solvatochromic shift method and microscopic solvent polarity parameter (ET N ) and results are compared. The kinetic stability and chemical reactivity of the selected molecules have been studied with the help of quantum chemical properties of the molecule and Frontier molecular orbital analysis using DFT.

Novel far UV–Vis absorbing bis(dihydrophenanthro[9,10-e][1,2,4]triazine) derivative dyes: Synthesis, optical, photophysical and solvatochromic properties

In this paper discussed novel fluorescent derivative dye in far UV–Vis range have been synthesized by bis-alkylation of starting compound 4, 12a-dihydrophenanthro [9, 10-e][1, 2,4]triazine-3(4H)-thione, with the appropriate dibromo compounds. and characterized by standard spectroscopic techniques. Their chemical structures were confirmed by 1HNMR, IR, MS and elemental analysis. Various optical characterizations were carried out in solvents of varying polarity. Optical parameters via extinction coefficient, absorption and emission cross-sections, fluorescence quantum yield, fluorescence lifetime, oscillator strength, the dipole moment, radiative decay rate constant, energy yield of fluorescence and the attenuation length has been determined. The effect of the spacer between two phenanthro[9,10-e][1,2,4]triazine units in new dye and solvent polarities upon the spectral properties are discussed. The ground-state (μg) and excited-state (μe) dipole moments were estimated using solvatochromic correlations. The higher value of Δμ may attribute to the singlet higher excited state of dyes which had strong intramolecular charge transfer character (ICT).

Synthesis, characterization and photophysical studies on novel benzofuran-3-acetic acid hydrazide derivatives by solvatochromic and computational methods

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 (ETN), 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.

Theoretical design, synthesis and studies on the solvatochromic behaviour of low band gap phenylenevinylene based copolymers

A new series of low band gap phenylenevinylene based copolymers was designed by employing density functional theory in the periodic boundary condition using HSE06 exchange correlation functional using 6-31G basis set and synthesized via the Gilch polymerization. The theoretical band gap of the copolymers MD-CA-PPV, MD-FL-PPV, MD-PT-PPV and MD-AN-PPV were found to be 1.98, 2.07, 2.31 and 1.99 eV respectively using the DFT/HSE06/6-31G calculation and the optical band gap of 1.96, 2.03, 2.01 and 1.98 eV respectively, according to the onset edge of lower energy peak of the polymers in solution. The experimental results supported the theoretical prediction. Solvatochromic behaviour of the synthesized copolymers was studied thoroughly in toluene/acetonitrile mixtures of varying polarity at room temperature. The absorption spectrum of the PPV polymers was sensitive to solvent effects which showed bathochromic and hypsochromic shifts with increasing solvent polarity indicating that the transitions involved were π-π* and n-π*. The ground and excited state dipole moments were calculated using solvatochromic correlations. Onsager radius determined from ab initio calculation was used in the determination of dipole moments. The change in the dipole moment (Δμ) was calculated both from solvatochromic shift method and on the basis of microscopic empirical solvent polarity parameter (ETN) and values are compared. It was observed that the excited state dipole moment (µe) was larger than its ground state (µg) counterpart. This indicated that a substantial redistribution of the π-electron densities occurred in the more polar excited state for the selected phenylenevinylene polymers. The third-order nonlinear optical (NLO) properties of the copolymers, evaluated by Z-scan method with nanosecond laser beam at 532 nm, are reported. The nonlinear absorption coefficient of the copolymers were calculated to be 0.17 × 10−10, 2.06 × 10−10, 0.63 × 10−10 and 2.83 × 10−10 esu, respectively for MD-CA-PPV, MD-FL-PPV, MD-PT-PPV and MD-AN-PPV which certified that the polymers showed semiconductor properties.

Photophysical and computational studies on optoelectronically active thiophene substituted 1,3,4-oxadiazole derivatives

In the present work, the photophysical properties of three novel optoelectronically active thiophene substituted 1,3,4-oxadiazole derivatives, namely 2-(4-(1H-inden-2-yl)phenyl)-5-(5-(1H-inden-2- yl) thiophen-2-yl)-1,3,4-oxadiazole [TIO], 2-(4-(thiophen-3-yl)phenyl)-5-(5-(thiophen-3-yl)thiophen-2-yl)-1,3,4-oxadiazole [TTO] and 2-(4-(benzo [b] thiophen-2-yl)phenyl)-5-(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)-1,3,4-oxadiazole [TPO] have been investigated. The ground and excited state dipole moments (μe) were determined experimentally by solvatochromic shift method using various solvatochromic correlations like Lippert’s, Bakhshiev’s, Kawski-Chamma-Viallet’s and solvent polarity parameter (ET N) equations. The ground state dipole moments (μg) were also estimated from ab initio computations using Gaussian 09 W software. It is observed that, the excited state dipole moments are higher than the ground state dipole moments for all the probe molecules. This indicates that, the probe molecules are more polar in the excited state than in the ground state. The HOMO-LUMO energy gap computed using density functional theory (DFT) and from absorption threshold wavelengths are found to be in good agreement. The chemical hardness (η) was determined for all the probes from HOMO-LUMO energies and results suggest the soft nature of the molecules. Further, the reactive centers like electrophilic site and nucleophilic site were identified with the help of molecular electrostatic potential (MESP) 3D plots using DFT computational analysis. Our preliminary investigations suggest that, the derivatives of 1,3,4-oxadiazoles namely TIO, TTO and TPO could play an important role in photonic, sensor and optoelectronic devices in future.

Solvent effect on the spectroscopic properties of 8EMOHCC

This paper reports the absorption and fluorescence spectra of ethyl 8-methoxy-2-oxo-2H-chromene-3-carboxylate 8EMOHCC has been recorded in various solvents of different polarities at room temperature. Solvatochromic shifts, specifically bathochromic (red) shifts were observed in the absorption and fluorescence spectra. The ground state dipole moment of 8EMOHCC was obtained from quantum chemical calculations. Solvatochromic correlations were used to estimate the ground state (µg) and excited state (µe) dipole moments. The quantum chemical calculations of ground state dipole moment is in good agreement with experimentally calculated ground state. The exited state (μe) dipole moments were estimated using Lippert’s, Bakhshiev’s and Kawski-Chamma-Viallet’s equations by using the variation of Stoke’s shift with the solvent polarity. The excited state dipole moments are observed to be greater than the ground state dipole moment, indicating a significant redistribution of the π-electron densities in excited state for 8EMOHCC. Finally bathochromic shift is observed upon increasing the polarity of the solvents for the molecule indicating π→π∗. ansition. Further, the change in dipole moments (Δµ) were calculated from solvatochromic shift method, microscopic solvent polarity parameter (ETN.)nd the value were correlated. The variations in spectra were analyzed by Kamlet-Taft parameters and it is observed that, the influence of HBD (β) is more than HBA (α) for emission process and Stoke’s shift, whereas the influence of HBD (β) is more than HBA (α) for absorption process for 8EMOHCC.

Study of the novel fluorescent 4-methyl-9-(3-oxobutanoyl)-2H,8H-pyrano[2,3-f]chromene-2,8-dione derivative. Estimation of the ground- and excited-state dipole moments from a solvatochromic shift

The optical properties of 4-methyl-9-(3-oxobutanoyl)-2H,8H-pyrano[2,3-f]chromene-2,8-dione was investigated in solvents of different polarity by employing UV–vis absorption and fluorescence spectroscopy at room temperature (298 K). A bathochromic shift is observed in absorption and fluorescence spectra of this molecule with increasing solvent polarity. Solvatochromic correlations were used to obtain the dipole moment in the ground and the first excited-state. The excited-state dipole moment was found to be larger than the ground-state dipole one.

Estimation of Ground-State and Singlet Excited-State Dipole Moments of Substituted Schiff Bases Containing Oxazolidin-2-one Moiety through Solvatochromic Methods

Absorption and fluorescence studies on novel Schiff bases (E)-4-(4-(4-nitro benzylideneamino)benzyl)oxazolidin-2-one (NBOA) and (E)-4-(4-(4-chlorobenzylidene amino)benzyl)oxazolidin-2-one (CBOA) were recorded in a series of twelve solvents upon increasing polarity at room temperature. Large Stokes shift indicates bathochromic fluorescence band for both the molecules. The photoluminescence properties of Schiff bases containing electron withdrawing and donating substituents were analyzed. Intramolecular charge transfer behavior can be studied based on the influence of different substituents in Schiff bases. Changes in position and intensity of absorption and fluorescence spectra are responsible for the stabilization of singlet excited-states of Schiff base molecules with different substituents, in polar solvents. This is attributed to the Intramolecular charge transfer (ICT) mechanism. In case of electron donating (-Cl) substituent, ICT contributes largely to positive solvatochromism when compared to electron withdrawing (-NO2) substituent. Ground-state and singlet excited-state dipole moments of NBOA and CBOA were calculated experimentally using solvent polarity function approaches given by Lippert-Mataga, Bakhshiev, Kawskii-Chamma-Viallet and Reichardt. Due to considerable π- electron density redistribution, singlet excited-state dipole moment was found to be greater than ground-state dipole moment. Ground-state dipole moment value which was determined by quantum chemical method was used to estimate excited-state dipole moment using solvatochromic correlations. Kamlet-Abboud-Taft and Catalan multiple linear regression approaches were used to study non-specific solute-solvent interaction and hydrogen bonding interactions in detail. Optimized geometry and HOMO-LUMO energies of NBOA and CBOA have been determined by DFT and TD-DFT/PCM (B3LYP/6-311G (d, p)). Mulliken charges and molecular electrostatic potential have also been evaluated from DFT calculations.

Photophysical properties of 3MPBA: Evaluation and co-relation between solvatochromism and quantum yield in different solvents

The present paper addresses the photophysical properties of 3-Methoxyphenyl boronic acid (3MPBA) by using solvatochromic shift and quantum chemical methods. The absorption and fluorescence spectra of newly synthesized aryl boronic acid derivative (3MPBA) have been recorded in various solvents of different polarities. The dipole moments were estimated using quantum chemical calculations and Solvatochromic correlations. It is observed that the excited state dipole moments (μe) are greater than the ground state dipole moment (μg) which confirms π→π* transition. And it is also observed that the ground state and excited state dipole moments are observed to be collinear to each other. The changes in dipole moment (Δμ) were also calculated both from solvatochromic shift method and microscopic solvent polarity parameter (ETN) and values are compared. The spectral variations were also analyzed by Kamlet-Taft parameters. It is found that HBA (β) influence is more than HBD (α) for ν̅a and ν̅f in alcohols whereas HBD (α) influence is more than HBA (β) for ν̅a and ν̅f in non alcohols. Further, the relative quantum yield (Φ), radiative and non-radiative decay constants are estimated by single point technique which concludes that the 3MPBA is more radiative in nature and less intersystem crossing and inter conversions are observed in the excited state.

Photophysical study of 6-amino-3-methyl-4-(4-nitrophenyl)-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile and estimation of ground-state and singlet excited-state dipole moments by solvatochromic approaches

An investigation of absorption and fluorescence behaviour of 6-amino-3-methyl-4-(4-nitrophenyl)-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (NDPPC) at room temperature was carried out using a series of twelve organic solvents with different polarities. Ground and excited state dipole moments were determined experimentally by using Lippert–Mataga polarity function, Bakhshiev solvent polarity parameter, Kawski-Chamma-Viallet solvent polarity parameter, Reichardt's microscopic solvent polarity parameter, Kamlet-Abboud-Taft multiple linear regression and Catalan dipolar polarizibility approach. Due to considerable π- electron density redistribution, the value of excited state dipole moment was found to be greater than that of the ground state. The ground state dipole moment value was determined by quantum chemical method which was used to estimate excited state dipole moment using solvatochromic correlations. Both non-specific solute-solvent interactions and hydrogen bonding interactions were investigated by using Kamlet-Abboud-Taft and Catalan method. TD-DFT (B3LYP/6-311G (d,p)) was used for the determination of HOMO-LUMO energies.