A density functional theory investigation on 1H-4-germapyridine-4-ylidene & the unsaturated heterocyclic substituted ones

In this computational survey, substituent effects of two fused benzene and two five-membered rings including pyrrole, phosphole, furan and thiophene are inspected through stability, aromaticity, charge distribution, global reactivity indexes of singlet (s) and triplet (t) germapyridines, at density functional theory (DFT). Results based on B3LYP/AUG-cc-pVTZ, M06-2X/6-311++G** and B3PW91/6-311++G** levels of theory, reveal: (1) The highest thermodynamic and kinetic stability is considered by germylene situated among two substituted furan rings, in a zigzag arrangement with the divalent center; (2) In spite of zigzag and/or chair arranged, the order of thermodynamically stabilization for fused rings is furan > thiophene > pyrrole > phosphole; (3) The substituted germylenes with two fused furan and thiophene rings, in zigzag or chair arrangement, exhibit more stability than unsubstituted germapyridine; (4) While two benzene rings destabilize the resulted germapyridine, two five-membered rings stabilize their corresponding N-heterocyclic germylenes (NHGes); (5) In all scrutinized structures, singlets appear as ground state, revealing more stability than their corresponding triplet congeners; (6) The most aromaticity character is considered for the substituted furan in a zigzag orientation towards the germapyridinic's nitrogen atom; (7) Atoms in molecules (AIM) analysis exhibits the highest electron density (rho(r) = 0.129) at bond critical point (BCP) of pyrrole and furan-fused NHGes in a zigzag arrangement. (8) Every NHGe reveals lower nucleophilicity and higher electrophilicity than the corresponding triplet congener; (9) The natural bond orbital (NBO) analysis exhibits the highest value of E-(2) for W-substituted furan singlet NHGe which is in consistent with the strongest inter-molecular bonding (IB). (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This computational study investigates the substituent effects on the stability and aromaticity of germanium heterocycles, with results showing that the substituted furan germylenes exhibit the highest stability and aromatic character.