Theoretical study on structures and stabilities of [H,Ge,C,N]

Theoretical investigations are performed for the first time on the simplest hydrogenated germanium cyanide [H,Ge,C,N], whose analogs [H,C₂,N] and [H,Si,C,N] have been detected in space and laboratory, respectively. The detailed potential energy surfaces in both singlet and triplet states are constructed at the CCSD(T)/6-311+G(3df,2p)//B3LYP/6-31G(d)+ZPVE level, including 18 minimum isomers and 26 interconversion transition states. The former three low-lying and kinetically stabilized isomers are HGeCN ¹1 (0.0 kcal/mol), HGeNC ¹2 (5.1 kcal/mol), and cyclic cCHNGe¹7 (11.1 kcal/mol). In addition, five isomers HCNGe ¹3 (33.8), HNCGe ¹5 (29.8), cNHCGe ¹8 (37.9), HGeCN ³1 (30.1), and HNCGe ³5 (26.5) each have considerable barriers, despite their high energies. Future laboratory characterization and astrophysical detection of the eight [H,Ge,C,N] isomers, especially the former three low-lying species ¹1, ¹2, and ¹7, are highly recommended. The accurate spectroscopic data at the QCISD/6-311 G(d,p) level are provided. For some species, the CBS-QB3 calculations are also performed. Wherever possible, comparisons with the analogous [H,C₂,N] and [H,Si,C,N] are made on the structural, energetic, and bonding properties.