Ground State Dipole Moments Research Articles

Determination of Excited Singlet-State Dipole Moments of Methoxy and Dimethylamino Substituted Benzylidenebenzosuberones Using Solvatochromic Method

The solvent effects on the electronic absorption and emission fluorescence spectra for a series of chalcone cyclic analogues were studied. The singlet-state excited dipole moments and the ground state dipole moments of the cyclic chalcone analogues E-2- benzylidene-1-benzosuberone E-2-(4′-methoxybenzylidene)-1-benzosuberone E-2-(4′-dimethylaminobenzylidene)-1-benzosuberone were calculated by using solvatochromic shift method by means of equations using the variations of Stokes’ shift with the solvent's dielectric constant and refractive index values. It was found that the excited state dipole moments calculated by the solvatochromic shift method were greater than the ground state dipole moments indicating a substantial redistribution of the pi-electron densities in a more polar excited state for each derivative.

Electron transport and nonlinear optical properties of substituted aryldimesityl boranes: a DFT study.

A comprehensive theoretical study was carried out on a series of aryldimesityl borane (DMB) derivatives using Density Functional theory. Optimized geometries and electronic parameters like electron affinity, reorganization energy, frontiers molecular contours, polarizability and hyperpolarizability have been calculated by employing B3PW91/6-311++G (d, p) level of theory. Our results show that the Hammett function and geometrical parameters correlates well with the reorganization energies and hyperpolarizability for the series of DMB derivatives studied in this work. The orbital energy study reveals that the electron releasing substituents increase the LUMO energies and electron withdrawing substituents decrease the LUMO energies, reflecting the electron transport character of aryldimesityl borane derivatives. From frontier molecular orbitals diagram it is evident that mesityl rings act as the donor, while the phenylene and Boron atom appear as acceptors in these systems. The calculated hyperpolarizability of secondary amine derivative of DMB is 40 times higher than DMB (1). The electronic excitation contributions to the hyperpolarizability studied by using TDDFT calculation shows that hyperpolarizability correlates well with dipole moment in ground and excited state and excitation energy in terms of the two-level model. Thus the results of these calculations can be helpful in designing the DMB derivatives for efficient electron transport and nonlinear optical material by appropriate substitution with electron releasing or withdrawing substituents on phenyl ring of DMB system.

Solvatochromic studies of biologically active iodinated 4-aryloxymethyl coumarins and estimation of dipole moments

The steady state absorption and emission spectra of biologically active iodinated 4-aryloxymethyl coumarins 4-(4-iodo-phenoxymethyl)-benzo[h]coumarin (4IPMBC) and 4-(4-iodo-phenoxymethyl)-6-methoxy coumarin (4IPMMC) are studied at room temperature in a series of solvents and 1,4-dioxane–acetonitrile solvent mixture. The effect of pure solvents upon the spectral properties are analyzed using Lippert–Mataga polarity function, Reichardt's microscopic solvent polarity parameter, Kamlet's and Catalan's multiple linear regression approaches. General solute–solvent interactions and hydrogen bonding interactions are operative in these systems. However, the contribution of later interaction is less. The solvatochromic data is used to estimate excited state dipole moment using experimentally determined ground state dipole moment. The bathochromic shift of emission spectra and increase in dipole moment after excitation indicate the intramolecular charge transfer (ICT) character in the emitting singlet state. The solvation studies in 1,4-dioxane–acetonitrile solvent mixture suggest that these dyes are preferentially solvated by 1,4-dioxane.

Fluorescence characteristics of aryl boronic acid derivate (PBA)

The absorption and fluorescence spectra of newly synthesized aryl boronic acid derivative namely Phenyl boronic acid (PBA) have been recorded in various solvents of different polarities. The ground state dipole moment of PBA was obtained from quantum chemical calculations. Solvatochromic correlations were used to estimate the ground state (μg) and excited state (μe) dipole moments. The excited state dipole moments are observed to be greater than the ground state dipole moments. Further, the ground and excited state dipole moments are not parallel but subtend by an angle of 70°. The changes in dipole moment (Δμ) were calculated both from solvatochromic shift method and microscopic solvent polarity parameter (ETN), and the values are compared. Solvent effects on the absorption and fluorescence spectra were quantified using Reichardt’s and bulk solvent polarity parameters were complemented by the results of the Kamlet–Taft treatment.

Experimental and computational approaches on dipole moment of 5-aminoisoquinoline

The ground and excited state (S1) dipole moments of 5-aminoisoquinoline (5-AIQ) are determined from solvatochromic shift method as a function of different solvent polarity functions. Dipole moment calculations using DFT and ab initio methods with different basis sets are performed. The experimental results show that the dipole moment in the excited state is higher than the ground state.

Solvent dependent photophysical properties of free base tetrapyridylporphyrin

Detail investigations are carried on the solvent dependent photophysical properties of free base tetrapyridylporphyrin by using steady state and time-resolved spectroscopic techniques at the ambient temperature (300K). The electronic absorption and emission spectra of free base tetrapyridylporphyrin are recorded in different organic solvents with varying polarity. The various transitions involved in the steady state measurements of free base tetrapyridylporphyrin are found to be mostly affected by the polarizability (Lorentz–Lorentz function leading to dispersive stabilization) rather than polarity (static dielectric constant leading to dielectric stabilization) of the solvents. The ground state dipole moment of free base tetrapyridylporphyrin is computed based on quantum chemical calculations. The difference in the excited state dipole moment and ground state dipole moment of free base tetrapyridylporphyrin is estimated from Lippert–Mataga and Bakhshiev equations. Interestingly, the fluorescence decay profiles of free base tetrapyridylporphyrin are found to follow a bi-exponential nature in different solvents.

Photophysical characteristics of two novel coumarin derivatives: Experimental and theoretical estimation of dipole moments using the solvatochromic shift method

The exited state (μe) dipole moment of a molecule is an important parameter, which gives information about electronic and geometrical structure of the molecule in the short-lived state. We have experimentally estimated the exited state (μe) dipole moment of two novel coumarin derivatives, namely, diethyl 2-acetamido-2-((6-methyl-2-oxo-2H-chromen-4-yl) methyl) malamute (DAM) and 5,6-Benzo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)] coumarin (5BDTC) by three methods, namely, Lippert’s, Bakhshiev’s, and Kawski–Chamma–Viallet’s. In the Solvatochromic shift method, spectral shift is due to internal excitation of the molecule. We have recorded absorption and emission spectra of the above two novel coumarin derivatives at room temperature using solvents of different polarities. The geometry of the molecules were fully optimized and the ground state dipole moment (μg) were also calculated theoretically by Gaussian 03 software using B3LYP/6-31g* level of theory. The excited state dipole moment was calculated using CIS/6-31G* level of theory. The μgand μewere calculated using the solvatochromic shift method and μewas also determined in combination with μg. It was observed that μewere greater than those of μg, indicating a substantial redistribution of the π-electron densities in a more polar excited state for this coumarin. Further, the changes in dipole moment (Δμ) were calculated both from the solvatochromic shift method and on the basis of microscopic empirical solvent polarity ([Formula: see text]) and the values are compared.

Synthesis, spectral behaviour and photophysics of donor–acceptor kind of chalcones: Excited state intramolecular charge transfer and fluorescence quenching studies

The spectral and photophysical properties of two chalcones containing electron donating and accepting groups with intramolecular charge transfer characteristics were synthesized and characterized by 1H NMR, 13C NMR and X-ray crystallography. Both compounds show very strong solvent polarity dependent changes in their photophysical characteristics, namely, remarkable red shift in the emission spectra with increasing solvent polarity, large change in Stokes shift, significant reduction in the fluorescence quantum yield; indicating that the fluorescence states of these compounds are of intramolecular charge transfer (ICT) character. The solvent effect on the photophysical parameters such as singlet absorption, molar absorptivity, oscillator strength, dipole moment, fluorescence spectra, and fluorescence quantum yield of both compounds have been investigated comprehensively. For both dyes, Lippert–Mataga and Reichardt’s correlations were used to estimate the difference between the excited and ground state dipole moments (Δμ). The interactions of dyes with colloidal silver nanoparticles (Ag NPs) were also studied in ethanol using steady state fluorescence quenching measurements. The fluorescence quenching data reveal that dynamic quenching and energy transfer play a major role in the fluorescence quenching of dyes by Ag NPs.

Synthesis and photophysical properties of novel chloroquinoline based chalcone derivates containing 1,2,3-triazole moiety

A series of novel chloroquinoline based chalcones containing 1,2,3-triazole moiety were synthesized. All new compounds were characterized by 1H NMR, 13C NMR, mass spectra and single crystal X-ray diffraction study. The absorbance, fluorescence spectra and quantum yield of all compounds were investigated in methanol. Photophysical properties of 1-(1-(7-chloroquinolin-4-yl)-5-methyl-1H-1,2,3-triazol-4-yl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (3a) were investigated in detail. The effect of various solvents over emission spectra of 3a was studied using Kamlet–Taft and Catalan polarity scales. The quantum yield of 3a in various solvents was also recorded. The ground state and excited state dipole moments of compound 3a were determined using solvatochromic methods. The ground state dipole moment was estimated to be 1.081D, while excited state dipole moment was found in the range of 11.969–3.801D. Thermal stability of compound 3a and its precursor was also investigated using thermogravimetric analysis.

Photophysical characteristics of biologically active 4-aryloxymethyl coumarins 4PTMBC and 1IPMBC

The absorption and fluorescence characteristics of biologically active coumarin derivatives 4-p-tolyloxymethyl-benzo[h]coumarin (4PTMBC) and 1-(4-iodo phenoxymethyl)-benzo[f]coumarin (1IPMBC) are studied at room temperature in a series of organic solvents and 1,4-dioxane – acetonitrile solvent mixture. The effect of pure solvents on the spectral properties are analyzed using Lippert–Mataga polarity function, Reichardt’s microscopic solvent polarity parameter, Kamlet’s and Catalan’s multiple linear regression approaches. Both general solute – solvent interactions and hydrogen bonding interactions are operative in these systems. However, the contribution of hydrogen bonding interactions is less compared to general solute–solvent interactions. The solvatochromic correlations are used to estimate excited state dipole moment using experimentally determined ground state dipole moment. The bathochromic shift of the emission spectra and the increase in excited state dipole moment indicate the intramolecular charge transfer (ICT) character in the emitting singlet state. The solvation studies in 1,4-dioxane – acetonitrile solvent mixture suggest that these dyes are preferentially solvated by 1,4-dioxane.

Estimation of ground and excited state dipole moments of synthesized coumarin derivative [N-(2-oxo-2H-chromen-4-yl)imino]triphenyl-phosphorane

Electronic absorption and fluorescence spectra of coumarin derivative [N-(2-oxo-2H-chromen-4-yl)imino] triphenyl phosphorane have been recorded at room temperature in wide range of solvents of different polarities. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas, a red shift in fluorescence emission maximum was observed. Synthesized compound [N-(2-oxo-2H-chromen-4-yl)imino] triphenyl phosphorane was characterized by 1H and 13C NMR, and FT-IR spectral studies. The ground and excited state dipole moments of molecule were obtained from Bakhshiev's and Bilot–Kawski's equations by means of the solvatochromic shift method. Very high value of dipole moment is observed for excited state as compared to ground state value and this is attributed to more polar excited state of the molecule. Numerical calculations are performed using B3LYP/6-31G+(d) and B3LYP/6-31G(d) level of theory for ground state in Gaussian 03. Studies in different solvents are also done using the CPCM method and UA0 radii with the same level of theory. A critical analysis between the values of dipole moment in gas phase and various solvents is also carried out for ground state.

"Estimation of ground and excited state dipole moments of aryl boronic acid derivative by solvatochromic shift method".

In the present work, the absorption and fluorescence spectra of newly synthesized aryl boronic acid derivative namely 2-Methylphenyl boronic acid (2MPBA) have been recorded in various solvents of different polarities. The ground state dipole moment of 2MPBA was obtained from quantum chemical calculations. Solvatochromic correlations were used to estimate the ground state (μ g ) and excited state (μ e ) dipole moments. The excited state dipole moments are observed to be greater than the ground state dipole moment and ground and excited state dipole moments are not parallel but subtend by an angle of 88(0). Further, the changes in dipole moment (Δμ) were calculated both from solvatochromic shift method and microscopic solvent polarity parameter (E T (N) ), and the value are compared. The spectral variations were analyzed by Kamlet-Taft parameters.

Solvent effects on the molecular resonance structures and photo-physical properties of a group of oxazine dyes

Absorption and fluorescence spectra of two oxazine dyes were recorded in various solvents in the range of 300–800nm, at room temperature. The solvatochromic behavior of these substances and their solvent–solute interactions, both specific and non-specific, was analyzed using linear solvation energy relationship concept, suggested by Kamlet–Taft. The ground and excited state dipole moments of these substances and molecular resonance structures were also evaluated by a solvatochromic shift method.

Solvents effect on the absorption and fluorescence spectra of 7-diethylamino-3-thenoylcoumarin: Evaluation and correlation between solvatochromism and solvent polarity parameters

Effect of solvents of varying polarities on absorption and fluorescence spectra and dipole moment of laser dye: 7-diethylamino-3-thenoylcoumarin (DETC) has been investigated. A small band shift is obtained in the absorption spectra compared to emission spectra. The spectral shifts were correlated with Catalan’s parameters using linear solvation energy relationship. It reveals that non-specific interaction measured by solvent polarity has more influence on absorption and solvent dipolarity contribution is significant in case of fluorescence. A bathochromic shift observed in absorption and emission spectra with increasing solvent polarity, which implied that the transition involved is π→π∗. The solvatochromic correlations were used to estimate the excited state dipole moment using experimentally determined ground state dipole moment. The observed single-state excited state dipole moment is found to be greater than the ground state.

Synthesis of novel carbazole fused coumarin derivatives and DFT approach to study their photophysical properties.

Novel coumarin derivatives have been synthesized by the classical Knoevenagel condensation of 4-hydroxy-9-methyl-9H-carbazole-3-carbaldehyde with active methylene compounds and characterized. Effect of solvent polarity on the photophysical properties, absorption and emission has been studied. The photophysical properties of the synthesized coumarins have been compared with some of the established analogous coumarin derivatives. Investigation of the structural parameters and understanding photophysical properties of the synthesized coumarin derivatives were carried out using Density Functional Theory (DFT) and Time Dependant Density Functional Theory (TDDFT) computations. The experimental values were correlated with the theoretical derived results. The ratio of the excited state and the ground state dipole moments was calculated by using solvatochromic and solvatofluoric data and compared with the values obtained from DFT and TDDFT computations.

Estimation of ground and excited state dipole moments of Oil Red O by solvatochromic shift methods

Absorption and fluorescence spectra of Oil Red O (abbreviated as ORO) are recorded in various solvents with different polarity in the range of 250–900nm, at room temperature. The solvatochromic shift methods have been used to determine the ground state (μg) and excited state (μe) dipole moments depending on dielectric constant and refractive index functions. It is observed that fluorescence spectra show positive solvatochromism whereas absorption spectra do not indicates sensitive behavior to solvent polarity. Excited state dipole moment is found as higher than those of ground state for all of the used methods and it is attributed to more polar excited state of ORO. Theoretical μg has been determined by quantum chemical calculations using DFT and semi empirical methods. HOMO, LUMO, molecular electrostatic potential (MEP) and solvent accessible surface of ORO are calculated by using DFT-B3LYP method.

Aggregation‐Induced Emission Activity in Iridium(III) Diimine Complexes: Investigations of Their Vapochromic Properties

Two iridium(III) diimine complexes [mono(1,10-phenanthroline)bis(triphenylphosphine)(dihydrido)iridium(III) hexafluorophosphate (1) and mono(1,10-phenanthroline)bis(triphenylphosphine)(hydrido)(chloro)iridium(III) hexafluorophosphate (2)] have been synthesized from a single two-step reaction. The structures of 1 and 2 both adopt distorted octahedral geometries, as established by single-crystal X-ray diffraction. The complexes, upon irradiation with UV light at 365 nm, emit faint light in solution and bright light in the solid state. The ground- and excited-state properties of these complexes were investigated through density functional theory (DFT) and time-dependent DFT calculations. The calculated energies for the transitions from the ground state to the singlet and triplet excited states were close to those determined from the experimental absorption and emission. Their molecular orbitals were also exploited to compute the ground-state dipole moments and redox potentials. Several experiments were performed to demonstrate the “aggregation-induced emission” (AIE) activity of these complexes. AIE was triggered by the restricted intramolecular rotation of the rotating units (phenyls in triphenyphosphines) in these molecules in the solid state. The solid thin films of 1 and 2 exhibit solvent-polarity-dependent vapour-responsive emission properties (vapoluminescent). The rationale for the different emission behavior in the solid state has been thoroughly investigated. The packing diagrams of 1 and 2 show that there is enough space available to accommodate small organic solvent molecules inside the crystal lattices.

Computations of absorption spectra and nonlinear optical properties of molecules based on anthocyanidin structure

Simulation of UV–VIS spectra and microscopic third-order nonlinear optical (NLO) coefficients at 532 nm wavelength of molecules based of anthocyanidin structure in gas phase environment using semi-empirical PM3 method was calculated. One-photon absorption characterizations of the investigated molecules have been theoretically obtained by configuration interaction method with doubly occupied molecular orbitals. Estimated theoretical spectra shows a sensibility to the different functional groups such as hydroxyl and methoxyl substitution in radicals. These groups causes red shift in absorption spectra in comparison to the other samples what agree well with the experimental data. Adjunction of such functional donor character group in the investigated molecule slightly decreases the HOMO–LUMO energy splitting gap but increases the ground state dipole moment resulting the substantial increase of NLO coefficient in this system comparing to the other samples. According to presented investigations the tested molecules have large nonlinear optical properties.

Estimation of ground and excited states dipole moments of α-hydroxy phenyl hydrazone derivatives: Experimental and quantum chemical methods

The ground state (μg) and excited state (μe) dipole moments of the studied α-hydroxy phenylhydrazones are determined by using solvatochromism theory which is based on the variation of Stokes shift with solvent's relative permittivity and refractive index. Excited state dipole moments are found as larger than the ground state dipole moment due to substantial redistribution of the π-electron density in more polar excited state. External electric field (EF) effect on HOMO–LUMO gap (HLG) and dipole moment is studied by GGA level of theory. Density of states (DOS) and HOMO, LUMO plots are also investigated by GGA method. Solvent accessible surface (SAS) and molecular electrostatic potential (MEP) are visualized as a result of DFT calculations.

NIR Emission in Borondifluoride Complexes of 2′-Hydroxychalcone Derivatives Containing an Acetonaphthone Ring

We report the synthesis of borondifluoride complexes of a series of 2′-hydroxychalcone derivatives containing the hydroxynaphthone ring. TD-DFT calculations confirm the charge transfer character of the lowest-energy transition band and reveal large values for the ground-state dipole moment. The fluorescence emission spectra in the solid state are considerably red-shifted relative to those in solution, leading to maximum emission wavelengths spanning from the far red to the NIR. The emission properties are clearly characteristic of tightly packed chromophores with strong excitonic coupling, as confirmed by X-ray structure analysis and electronic absorption spectroscopy. The optical properties of the six dyes 1-BF2–6-BF2 are discussed in terms of interchromophoric interactions in the crystal and dipole moment values. Dyes 3-BF2 and 4-BF2 emit light at 690 and 751 nm with 13% and 6.5% efficiencies, respectively, and as such they represent very appealing materials. Compound 6-BF2 presents an emission maximum ...