Novel triplet germylenes in focus: normal vs. abnormal triplet exocyclic tetrazol-5-vinylidene germylenes at DFT.

Substituent effects on stability (assumed as the singlet and triplet energy gaps, ΔΕS-T) of novel 1,4-disubstituted-tetrazole-5-vinylidene germylenes (normal, 1R) and their corresponding 1,3-disubstituted-tetrazole-5-vinylidene germylenes (abnormal, 2R) are computed and compared, at B3LYP/6-311++G** and M06/6-311++G**, where R = H, CN, CF3, F, SH, C6H6, OMe, and OH. Interestingly, every triplet vinylidene germylene shows more stability than its corresponding singlet. Also, every triplet abnormal isomer (2R) emerges to be more stable than its corresponding normal (1R). All abnormal 2R isomers show broader band gaps (ΔEHOMO-LUMO) and higher nucleophilicity (N), but less electrophilicity (ω) than their corresponding normal 1R isomers. The NICS (nuclear-independent chemical shift) results indicate that every 1R (except singlet 2Ph) emerges more aromatic than its corresponding 2R. Our Hammet studies indicate that 1R is more sensitive to the electronic effects of substituents, R, than 2R. Electron-donating species increase N in both 1R and 2R, while electron-withdrawing groups increase stability.