Substituent effects on the stability of N-heterocyclic germylenes using density functional theory

The effects of one and two fused six-membered heterocyclic rings on properties of novel singlet and triplet germylenes are studied, at density functional theory (DFT). The aim of the present work is to recognize the influence of nitrogen and phosphorus heteroatoms along with germylene center (GeC) on the stability, band gap, polarity, polarizability, electrophilicity, nucleophilicity, and charge. Irrespective of ortho or para organization, fusion of one pyridine and phosphinine ring causes more vibration frequency, stabilizing influence, and polarizability than two fused ones. The natural bond orbital (NBO) analysis of one fused germylenes displays covalent bonds with different powers between nitrogen and phosphorus heteroatoms with germylene center. They show different occupancy number for lone pair on the heteroatoms at ortho or para position. Also, because of dissimilar interactions of LPN8 ->sigma*(C3-Ge16), sigma(C3-Ge16)->sigma*(C2-N6), LPP16 ->sigma*(C3-Ge15), and sigma(C3-Ge15)->sigma*(C2-P16), they have different stabilization energy (E-(2)). There is a good consistency between singlet-triplet energy separation (Delta Es-t = E-t - E-s) and E-(2) values. The stability based on Delta Es-t and E-(2) values of para-one fused germapyridines is more than the ortho-ones.