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The synthesis and the studies of optical and electronic properties of new bis‐indenone‐fused tetraazaanthracene isomers as electron accepting materials are reported. TD‐DFT calculations have been also undertaken and corroborate experiments. Organic field effect transistors demonstrated unipolar n‐type characteristics and average electron mobility values. [ABSTRACT FROM AUTHOR]

A detailed insight behind the structure of absorption bands of the photochromic couple dimethyldihydropyrene (DHP)/metacyclophanediene (CPD) is studied employing vibronic coupling theory. Two separate model molecular Hamiltonians, including a maximum of four electronic states and 18 vibrational modes for DHP and five electronic states and 20 vibrational modes for CPD, are constructed in a diabatic electronic representation. The parameters of the Hamiltonians are estimated from the electronic energies obtained from extensive density functional theory (DFT) and time-dependent DFT calculations. Based on these Hamiltonians' parameters, a detailed analysis of potential energy curves is performed in conjunction with positional and energetic locations of several stationary points in multi-dimensional potential energy surfaces. Based on the results of electronic structure calculations, quantum nuclear dynamics studies on the electronic excited states of DHP and CPD are performed to understand the impact of non-adiabatic effects on the formation of vibronic structures of absorption bands of these photo-isomers. [ABSTRACT FROM AUTHOR]

Vibronic coupling in the first eight electronic excited states of Pentafluorobenzene (PFBz) is investigated in this article. In particular, the vibronic coupling between the optically bright ππ* and optically dark πσ* states of PFBz is considered. A model 8 × 8 diabatic Hamiltonian is constructed in terms of normal coordinate of vibrational modes using the standard vibronic coupling theory and symmetry selection rule. The Hamiltonian parameters are estimated with the aid of extensive ab initio quantum chemistry calculations. The topography of the first eight electronic excited states of PFBz is examined at length, and multiple multi-state conical intersections are established. The nuclear dynamics calculations on the coupled electronic surfaces are carried out from first principles by the wave packet propagation method. Theoretical results are found to be in good accord with the available experimental optical absorption spectrum of PFBz. [ABSTRACT FROM AUTHOR]

Photodetachment spectroscopy of H2B-7 and its deuterated isotopomer probing the energetically low-lying electronic states of the respective neutral cluster is theoretically investigated in this paper. The theoretical methodology is based on detailed quantum chemistry calculations of electronic state energies, construction of a vibronic coupling model in the diabatic electronic basis, and nuclear dynamics calculations from first principles using time-dependent and time-independent quantum mechanical methods. The theoretical model consists of five coupled electronic states and fifteen vibrational modes. Several reduced dimensional calculations are performed to identify the relevant vibrational modes contributing to the vibronic structure of electronic bands and the impact of non-adiabatic coupling on them. The low-energy part of the spectrum of both H2B7 and its deuterated analogue is assigned by examining the vibronic wavefunctions and the results are compared with the experimental findings. The nonadiabatic decay dynamics of the electronic excited states of the neutral clusters is examined at length. [ABSTRACT FROM AUTHOR]

The primary goal of the present article is to provide an unbiased structural confirmation of C2B5−, relying on its available experimental photo-detachment spectra. The study is performed from scratch by optimizing the lowest energy isomers of C2B5− and later, suitable molecular vibronic Hamiltonians are constructed by analyzing the normal modes of these optimized isomers. The Hamiltonians' parameters are evaluated from the fits of the calculated ab initio single point energies using a state of the art multireference configuration (MRCI) level of theory employing a correlation consistent polarized triple zeta (cc-pVTZ) basis set. The state-averaged variant of the MRCI level of theory is also applied to deal with the highly interactive electronic states of both of the isomers. A detailed analysis of the potential energy curves along the totally symmetric vibrational modes is performed to understand the energy modulation between the different electronic states and also to find the energetic locations of the conical intersections. The introduction of the non-symmetric vibrational modes in the Hamiltonians help to understand the impact of non-adiabaticity during energy modulation in the coupled surfaces. Later, both adiabatic and non-adiabatic nuclear dynamics are performed on the electronic states of both of the isomers using the constructed reduced and full-dimensional Hamiltonians. The results of the adiabatic dynamics are used to assign the positions of the simulated photo-detachment bands, while the non-adiabatic dynamics improve the shape of those bands. Finally, we compare our theoretical findings with the available experimental photo-detachment spectra of C2B5− to provide an unbiased structural confirmation of the participating isomers of C2B5− in its photo-detachment spectra. [ABSTRACT FROM AUTHOR]

The nuclear dynamics of the low-lying first four electronic states of the prototypical indenyl radical is investigated based on first principles calculations to rationalize the experimental vibronic structure of the radical. The study is performed following both time-dependent and time-independent quantum-chemistry approaches using a model diabatic Hamiltonian. The construction of model Hamiltonians is based on the fits of the adiabatic energies calculated from the electronic structure method. The analyses of the static and dynamics results of the present study corroborate the experimental findings regarding the shape of the spectrum, vibrational progressions and the lifetime of the excited state. Finally, the present theoretical investigations suggest that the electronic non-adiabatic effect is extremely important for a detailed study of the vibronic structure and the electronic relaxation mechanism of the low-lying electronic states of the indenyl radical. [ABSTRACT FROM AUTHOR]

Abstract: The molecular structure, thermal stability, detonation properties and impact sensitivity of nitrogen‐rich tetrazine‐based designed high energy density molecules are examined. The effective stability of the designed molecules in terms of electronic structure, thermal excitation, photo‐excitation and in presence of water are predicted. The topography of the excited and ground state (S1 and S0) of those molecules along the C−NO2 bond dissociation coordinate are studied. The existence of the double minima at the S1 state and the S1‐S0 intersection produces a probabilistic path for molecules B1, B2 and A1, to revert back to their respective S0 state from the S1 state via both radiative and non‐radiative deactivation mechanism. The energy content (in terms of heats of formation), detonation velocities and detonation pressure of tetrazine‐based molecules are measured. Interestingly, the thermal stability of these designed molecules is higher than the two well‐known high energy density molecules: RDX and HMX. The detonation velocities and the detonation pressure of these molecules are higher than RDX, however, are lower than HMX. In addition, the safety, reliability and stability of these high energy density molecules have been measured by formulating semi‐empirical equations of impact sensitivity based on linear and multiple linear regression method and the present study is ended with the discussion of most probable synthetic routes to the designed molecules. [ABSTRACT FROM AUTHOR]

In continuation to our earlier work [Sarkar et al., Mol. Phys. 2015, 113, 3073-3084], we present here the vibronic structure and nonradiative decay dynamics of energetically low-lying electronic states of CH2F2+. Interesting comparison is made with the results obtained for the deuterated isotopomer CD2F2+. The results are compared with both broad band as well as high-resolution experimental spectroscopy data available in the literature. The progression of vibrational modes in the spectra is identified, assigned and discussed in relation to the assignments available in the literature. Both time-independent and time-dependent quantum mechanical methods are used to carry out nuclear dynamics calculations. The underlying potential energy surfaces and their coupling surfaces are constructed by rigorous ab initio quantum chemistry calculations. [ABSTRACT FROM AUTHOR]

Two bis(quinoxaline-dithiolato)nickel(III) complexes [Bu4N]-[NiIII(6,7-qdt)2] (1; 6,7-qdt = quinoxaline-6,7-dithiolate) and [Ph4P][NiIII(Ph26,7-qdt)2]·CHCl3 (2; Ph26,7-qdt = diphenylquinoxaline-6,7-dithiolate) have been synthesized from their NiII analogues by iodine oxidation. Compounds 1 and 2 have been characterized by routine spectral analysis and singlecrystal X-ray structure determination. Nickel(III) complexes 1 and 2 exhibit redshifted absorption bands compared with their NiII analogues; the electronic absorption spectral studies have been corroborated by DFT calculations. Electro-chemical studies on 1 and 2 are consistent with those of their NiII analogues. Electron spin resonance (ESR) studies confirm that nickel is present in both 1 and 2 in its +3 oxidation state. This is also consistent with the fact that only one cation (Bu4N+ for 1 and Ph4P+ for 2) is present in the respective crystal structures. The crystal structures of both compounds are characterized by C-H···S and C-H···N hydrogen-bonding interactions. Hirshfeld surface analyses have been studied to gain deep insight into the hydrogen-bonding interactions around/among the coordination complex anions. [ABSTRACT FROM AUTHOR]

High-valent oxoiron species have been invoked as oxidizing agents in a variety of iron-dependent oxygenases. Taking inspiration from nature, selected nonheme iron complexes have been developed as catalysts to elicit C-H oxidation through the mediation of putative oxoiron(V) species, akin to those proposed for Rieske oxygenases. The addition of carboxylic acids in these iron-catalyzed C-H oxidations has proved highly beneficial in terms of product yields and selectivities, suggesting the direct involvement of iron(V)-oxo-carboxylato species. When the carboxylic acid functionality is present in the alkane substrate, it acts as a directing group, enabling the selective intramolecular γ-C-H hydroxylation that eventually affords γ-lactones. While this mechanistic frame is solidly supported by previous mechanistic studies, direct spectroscopic detection of the key iron(V)-oxo-carboxylato intermediate and its competence for engaging in the selective γ-C-H oxidation leading to lactonization have not been accomplished. In this work, we generate a series of well-defined iron(V)-oxo-carboxylato species ( 2c - 2f ) differing in the nature of the bound carboxylate ligand. Species 2c - 2f are characterized by a set of spectroscopic techniques, including UV-vis spectroscopy, cold-spray ionization mass spectrometry (CSI-MS), and, in selected cases, EPR and Mössbauer spectroscopies. We demonstrate that 2c - 2f undergo site-selective γ-lactonization of the carboxylate ligand in a stereoretentive manner, thus unequivocally identifying metal-oxo-carboxylato species as the powerful yet selective C-H cleaving species in catalytic γ-lactonization reactions of carboxylic acids. Reactivity experiments confirm that the intramolecular formation of γ-lactones is in competition with the intermolecular oxidation of external alkanes and olefins. Finally, mechanistic studies, together with DFT calculations, support a mechanism involving a site-selective C-H cleavage in the γ-position of the carboxylate ligand by the oxo moiety, followed by a fast carboxylate rebound, eventually leading to the selective formation of γ-lactones., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

A series of heptamethine-oxonol dyes featuring different heterocyclic end groups were designed with the aim to explore structure-property relationships in π-extended coupled polymethines. These dyes can be stabilised under three different protonation states, affording dicationic derivatives with an aromatic core, cationic heptamethines, and zwitterionic bis-cyanine forms. The variation of the end groups directly impacts the absorption and emission properties and mostly controls reaching either a colourless neutral dispirocyclic species or near-infrared zwitterions. The acidochromic switching between the three states involves profound electronic rearrangements leading to notable shifts of their optical properties that were investigated using a parallel experiment-theory approach, providing a comprehensive description of these unique systems., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The presence of nonadiabaticity in the photodetachment bands of the anionic mixed carbon-boron cluster C 3 B 5 - has been realized through ab initio electronic structure calculations and detailed analyses of quantum dynamics study on top of those electronic structures. In the course of our study, we traverse extensive first principles electronic structure calculations to compute potential energy curves and to trace the energetic locations for the conical intersections in the multidimensional surfaces. All the ab initio calculations are performed on the four low-lying electronic states of the C 3 B 5 cluster, while quantum nuclear dynamics are pursued on those electronic states by applying both time-dependent and time-independent quantum chemistry frameworks. In particular, we rely on the diabatic electronic representation to construct the molecular Hamiltonian. Altogether, the simulated theoretical spectra offer exceptional agreement with the experimental attainments.

We designed and synthesized a novel di(benz[ f ]indenone)-fused tetraazaanthracene derivative and isolated its two isomers, 1a and 1s , having anti and syn configurations, respectively. Their structure and that of the condensation reaction intermediates, anti - 2a and syn - 2s , were fully characterized using one- and two-dimensional nuclear magnetic resonance spectroscopy and single-crystal X-ray diffraction. The optical and electronic properties of 1a and 1s were investigated using ultraviolet-visible absorption and fluorescence spectroscopies, cyclic voltammetry, and time-dependent density functional theory calculations. The presence of the carbonyl and ethynyltris(isopropyl)silane groups endows the di(benzoindenone)-fused azaacene derivatives with a strong electron accepting character. With an electron affinity of approximately -3.7 eV, the two isomers represent attractive electron-deficient molecular systems for the generation of n -channel semiconducting materials. Organic field effect transistors of 1a and 1s showed electron transport, and organic solar cells gave a proof of concept of the potential of the two compounds as electron acceptor materials when they are paired with an electron donor polymer.

The primary goal of the present article is to provide an unbiased structural confirmation of C2B5-, relying on its available experimental photo-detachment spectra. The study is performed from scratch by optimizing the lowest energy isomers of C2B5- and later, suitable molecular vibronic Hamiltonians are constructed by analyzing the normal modes of these optimized isomers. The Hamiltonians' parameters are evaluated from the fits of the calculated ab initio single point energies using a state of the art multireference configuration (MRCI) level of theory employing a correlation consistent polarized triple zeta (cc-pVTZ) basis set. The state-averaged variant of the MRCI level of theory is also applied to deal with the highly interactive electronic states of both of the isomers. A detailed analysis of the potential energy curves along the totally symmetric vibrational modes is performed to understand the energy modulation between the different electronic states and also to find the energetic locations of the conical intersections. The introduction of the non-symmetric vibrational modes in the Hamiltonians help to understand the impact of non-adiabaticity during energy modulation in the coupled surfaces. Later, both adiabatic and non-adiabatic nuclear dynamics are performed on the electronic states of both of the isomers using the constructed reduced and full-dimensional Hamiltonians. The results of the adiabatic dynamics are used to assign the positions of the simulated photo-detachment bands, while the non-adiabatic dynamics improve the shape of those bands. Finally, we compare our theoretical findings with the available experimental photo-detachment spectra of C2B5- to provide an unbiased structural confirmation of the participating isomers of C2B5- in its photo-detachment spectra.

The nuclear dynamics of the low-lying first four electronic states of the prototypical indenyl radical is investigated based on first principles calculations to rationalize the experimental vibronic structure of the radical. The study is performed following both time-dependent and time-independent quantum-chemistry approaches using a model diabatic Hamiltonian. The construction of model Hamiltonians is based on the fits of the adiabatic energies calculated from the electronic structure method. The analyses of the static and dynamics results of the present study corroborate the experimental findings regarding the shape of the spectrum, vibrational progressions and the lifetime of the excited state. Finally, the present theoretical investigations suggest that the electronic non-adiabatic effect is extremely important for a detailed study of the vibronic structure and the electronic relaxation mechanism of the low-lying electronic states of the indenyl radical.

Photodetachment spectroscopy of H 2 B 7 - and its deuterated isotopomer probing the energetically low-lying electronic states of the respective neutral cluster is theoretically investigated in this paper. The theoretical methodology is based on detailed quantum chemistry calculations of electronic state energies, construction of a vibronic coupling model in the diabatic electronic basis, and nuclear dynamics calculations from first principles using time-dependent and time-independent quantum mechanical methods. The theoretical model consists of five coupled electronic states and fifteen vibrational modes. Several reduced dimensional calculations are performed to identify the relevant vibrational modes contributing to the vibronic structure of electronic bands and the impact of non-adiabatic coupling on them. The low-energy part of the spectrum of both H 2 B 7 and its deuterated analogue is assigned by examining the vibronic wavefunctions and the results are compared with the experimental findings. The nonadiabatic decay dynamics of the electronic excited states of the neutral clusters is examined at length.