Journal of Chemical Sciences最新文献

Resultant concepts in information theory (IT) combine probability and current contributions, due to the modulus and phase of molecular state, respectively. Classical (probability) and resultant (wavefunction) descriptors are summarized and relations between entropy and information densities are investigated. The connection between the Shannon and Fisher measures is commented upon and quantum-generalized. The gradient of entropy-density determines the amplitude of the local information-content, the squared gradient of the wavefunction-logarithm. The discrete and continuous probability and improbability descriptors are compared and their normalizations explored. The symmetric binary channel of communication theory, the IT model of an elementary chemical bond, is reexamined and its complementary probability (signal-switching) and improbability (signal-conservation) entropies are interpreted as the orbital-uncertainty (“noise”, covalency) and orbital-certainty (“determinicity”, iconicity) descriptors. Localization/delocalization terms in the binary entropy function are identified and additive and nonadditive bond components are extracted.

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Classical and nonclassical entropy and information measures, probability andimprobability descriptors, and components of chemical bonds, along with thesymmetric binary channel of communication theory.

We investigated the shape resonances of DNA and RNA nucleobases using time-dependent density functional theory (TD-DFT). Benchmark calculations are conducted on gas-phase thymine using a range of DFT functionals to identify the most suitable one for subsequent studies. Resonance transition energies are obtained through the TD-DFT/RVP stabilization method and compared with EA-EOM-DLPNO-CCSD reference values to evaluate the performance of various functionals. The comparison reveals that CAM-B3LYP yields the smallest deviations relative to the EA-EOM-DLPNO-CCSD/RVP results. Consequently, resonance positions and widths for all DNA and RNA nucleobases are computed using stabilization plots generated with the TD-DFT with CAM-B3LYP functional. The calculated resonance positions for low-lying resonance states of all nucleobases are within ±0.4 eV of those from the EA-EOM-DLPNO-CCSD method, except for the high-lying 3π* and 4π* resonance of adenine. Resonance widths are largely underestimated, except for cytosine.

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The gas phase acidities of phenol C₆H₅OH, benzoic acid C₆H₅COOH and o-, m-, and p-hydroxybenzoic acids HOC₆H₄COOH were calculated at the MP2/6-31+G(d) and CAM-B3LYP/6-31+G(d,p) levels of theory and the values were closed with the experimental (Delta_{acid} G^{0}) values reported in the literature. The resonance effect operating in the acidity properties of the molecules were studied by analyzing the electronic density in terms of the Fukui function of their anionic compounds C₆H₅O(−), C₆H₅COO(−), o-, m-, and p-(−)OC₆H₄COOH and o-, m-, and p-OC₆H₄COO(−). The Fukui function f ⁻(r) for electrophilic attack explained the effect and suggested how the resonance contribution describe the anions stability.

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Analysis of charge delocalization in the phenoxide and carboxylate anions of p-hydroxybenzoic acid using the Fukui function for electrophilic attack

A comparative analysis between the procedure originally followed to establish the local hardness concept and a recent one based on a local chemical potential, defined within the grand canonical ensemble formalism, is done to get a better understanding of the main aspects involved in both procedures and to show that the local and non-local counterparts of global reactivity descriptors recently developed, constitute an excellent complement to analyze chemical reactivity within the framework of conceptual density functional theory.

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A comparative analysis between the procedure originally followed to establish the local hardness and the hardness kernel concepts and a recent one based on a local chemical potential, defined within the grand canonical ensemble formalism, is done. The original local softness and softness kernel remain unchanged.

This work emphasizes the potential of (benzo)chalcogenadiazole in recognizing anions via chalcogen bonding as a key interaction. We employed various theoretical tools to analyse the binding affinity and selectivity of substituted (benzo)thiadiazole for fluoride. The molecular electrostatic potential surface provided qualitative insights into the influence of substituents on electronic properties and the (sigma ) hole of the sulfur atom in directing the interaction strength with the anionic counterpart. Quantitative evaluations using symmetry-adapted perturbation theory, natural bond orbital analysis and topological descriptors at bond critical points confirmed the interaction mechanisms. Notably, the study revealed that the S···F^- bond strength was moderately enhanced for bis(trifluoromethyl)thiadiazole compared to tetrafluorobenzothiadiazole. Finally, the significant S···F^- bond was found to exhibit a partial covalent character, which has important implications for the design of novel chalcogenadiazole-derived anion receptors and sensors, contributing to the advancement of anion recognition.

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