Tuning ‘Stokes Shift’ and ICT Character by Varying the Donor Group in Imidazo[1,5 a]pyridines: A Combined Optical, DFT, TD‐DFT and NLO Approach

Mohbiya, Dhanraj R.; Sekar, Nagaiyan

doi:10.1002/slct.201702579

Cited by 40 publications

(33 citation statements)

References 68 publications

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“…For the D–A π‐conjugated dyes system, the energy band gap depends on the factors such as the donor‐acceptor substitution pattern and donor‐acceptor strength. Hence, a rise in the donor‐acceptor strength consequently would favor a decrease in the band gap energy . Therefore, a suitable selection of donor and acceptor groups can effectively reduce the energy band gap leading in effective CT features within the fluorophores.…”

Section: Resultsmentioning

confidence: 99%

“…Hence, a rise in the donor-acceptor strength consequently would favor a decrease in the band gap energy. [114] Therefore, a suitable selection of donor and acceptor groups can effectively reduce the energy band gap leading in effective CT features within the fluorophores. Molecular electrostatics potential (MEP) surface determination is crucial as it aids to correlate charge properties with electron density distribution on the fluorophore by virtue of positive or negative electrostatic potential surfaces.…”

Section: Electronic Transitions Frontier Molecular Orbitals (Fmo) Anmentioning

confidence: 99%

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N‐Ethyl Carbazole Derived D‐π‐A‐π‐D Based Fluorophores: Consolidated Spectroscopic, Viscosity and DFT Studies

2019

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This article reports design and synthesis of three new fluorophores (5 a‐c) with the donor‐π‐acceptor‐π‐donor motif, where dicyano vinylene group is the central acceptor, N‐ethyl carbazole group is a fixed donor and varying the N‐substituted secondary donors so as to study their photophysical behavior. Based on the systematic photophysical and theoretical reconnaissances, the fluorophores structure‐property relationships are defined. Their spectral and photophysical behaviors are affected by the solvent polarity, with a significant bathochromic shift in emission and large Stoke shifts being observed in polar solvents. Contrary to dipolar asymmetric analogue this system shows an efficient intramolecular charge transfer as observed from various solvent polarity plots. For 5 a, 5 b, and 5 c, the viscosity induced emission studies show respectively 3.78, 6.53, and 6.82 times enhancement in their fluorescence intensity and hence act as a fluorescent molecular rotor (FMR). The structure and electronic properties of these fluorophores were evaluated using density functional theory computations using B3LYP/6‐311++G(d,p). The frontier molecular orbitals and the optimized geometry reveal that secondary donors in each fluorophore donate the electron and not the N‐ethyl carbazole group which is more twisted. The non‐linear and linear optical properties were determined employing solvatochromic and computational methods in solvents of varying polarities with results falling within the expected limiting values. The linear and non‐linear optical properties of the fluorophores change with the strength of different secondary donors used and solvent polarity. The two photon absorption cross‐section described using two level approximation is highest for 5 b (115‐172 GM).

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Section: Resultsmentioning

confidence: 99%

Section: Electronic Transitions Frontier Molecular Orbitals (Fmo) Anmentioning

confidence: 99%

N‐Ethyl Carbazole Derived D‐π‐A‐π‐D Based Fluorophores: Consolidated Spectroscopic, Viscosity and DFT Studies

2019

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“…In recent years, theoretical estimation of NLO properties of complex organic molecules to establish the influence of individual moieties with aid of DFT calculation are under recent attraction. Various molecular structural parameters, molecular electrostatic potential map, charge transfer interaction and NLO property of various molecules were analysed by DFT method and using Natural bond orbital analysis . Notable report includes the establishment of role of halogen substituents in tuning the NLO properties of cycloparaphenylenes (CPP) and theoretical estimation shows high NLO values was obtained when one half of each CPP was substituted in halo CPP .…”

Section: Introductionmentioning

confidence: 99%

“…The solvent‐induced effects on the NLO of new pyrrole‐pyrazoline derivatives were studied using self‐consistent reaction field method in which increase in nonlinear absorption coefficient with solvent polarity was explained . The structural and electronic properties of imidazo pyridine derivatives were evaluated at B3LYP/6‐311++G(d,p) level to elucidate their large Stokes shifts as well as NLO parameters in solvents of different polarities . The bell‐shape behaviour of second hyperpolarizability of the asymmetric hetero‐phenalenyl dimers was theoretically investigated and it was clarified by the new definition of diradical/ionic characters .…”

Section: Introductionmentioning

confidence: 99%

“…Various molecular structural parameters, molecular electrostatic potential map, charge transfer interaction and NLO property of various molecules were analysed by DFT method and using Natural bond orbital analysis. [19][20][21][22][23][24][25] Notable report includes the establishment of role of halogen substituents in tuning the NLO properties of cycloparaphenylenes (CPP) and theoretical estimation shows high NLO values was obtained when one half of each CPP was substituted in halo CPP. [19] The solventinduced effects on the NLO of new pyrrole-pyrazoline derivatives were studied using self-consistent reaction field method in which increase in nonlinear absorption coefficient with solvent polarity was explained.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropic Nonlinear Optical and Optical Limiting Studies of an Ethylenediamminium Picrate Crystal with Femtosecond Excitation

Chandrasekar¹,

Rajan²,

Soma

et al. 2020

ChemistrySelect

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Femtosecond laser excitation (800 nm, ∼150 fs, 80 MHz) induced anisotropic nonlinear optical behaviour and optical limiting action of ethylenediamminium picrate (EDAPA) crystal along two prominent orientations (2 0 0) and (1 1 1) was studied using the Z‐scan technique. EDAPA exhibited reverse saturable type nonlinear absorption ascribed to two‐photon absorption (2PA) process and self‐defocusing based on nonlinear refraction. Intensity dependent nonlinear absorption studies portray the 2PA coefficient is independent of the peak intensity of excitation. Frontier molecular orbitals studies revealed the non‐availability of real states at laser excitation (1.55 eV) and the measured energy gap of 3.18 eV avails the energy states for simultaneous absorption of two photons involving virtual states leading to the occurrence of genuine 2PA. In addition, using molecular electrostatic potential (MEP) analyses polarizability (5.30×10−24 esu) and dipole moment (7.317 Debye) were calculated using the density functional theory. A variation in the NLO coefficients with respect to orientation of excitation arises due to the anisotropy of the crystal. EDAPA crystal along (1 1 1) orientation has high laser damage threshold (9.1 GW/cm2) and low optical limiting threshold (24.36 μJ/cm2) and thus the wide dynamic range make it a preferred candidate towards laser safety devices for high repetition rate ultrashort laser pulse excitation.

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Luminescent Imidazo[1,5‐a]pyridine Scaffold: Synthetic Heterocyclization Strategies‐Overview and Promising Applications

Volpi

2022

Asian J Org Chem

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In the last few years, imidazo[1,5‐a]pyridine derivatives have attracted growing attention due to their remarkable emissive behaviours, structural modification and biological properties. Previously published works emphasize the possible technological applications of this luminescent scaffold and demonstrate the stringent relationship between chemical substituents and optical properties. The main goal of this work is to provide a complete list of the reported achievements concerning these promising heterocyclization reactions obtained starting from a huge variety of reagents, catalysts, oxidants, dehydrating agents involved in various reaction conditions. Particular attention is focused on the final possible substitutions, conjugations and structural modifications of the reported synthetic approaches, a powerful aspect to design innovative and employable new luminescent imidazo[1,5‐a]pyridine products.

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Tuning ‘Stokes Shift’ and ICT Character by Varying the Donor Group in Imidazo[1,5 a]pyridines: A Combined Optical, DFT, TD‐DFT and NLO Approach

Cited by 40 publications

References 68 publications

N‐Ethyl Carbazole Derived D‐π‐A‐π‐D Based Fluorophores: Consolidated Spectroscopic, Viscosity and DFT Studies

N‐Ethyl Carbazole Derived D‐π‐A‐π‐D Based Fluorophores: Consolidated Spectroscopic, Viscosity and DFT Studies

Anisotropic Nonlinear Optical and Optical Limiting Studies of an Ethylenediamminium Picrate Crystal with Femtosecond Excitation

Luminescent Imidazo[1,5‐a]pyridine Scaffold: Synthetic Heterocyclization Strategies‐Overview and Promising Applications

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