Hydrogen and covalent bonding in H2BHX and H2BXH (X = CN and NC) dimers and cooperative effect in H2BHXHX and H2BXHXH trimers

Quantum chemical calculations have been performed to investigate the interaction of the neutral H2B radical with hydrogen cyanide (HCN) and hydrogen iso-cyanide (HNC) at the MP2/aug-cc-pVTZ level. The results show that a weak hydrogen bond and a strong covalent interaction can be formed between the two molecules. In H2BHCNHCN and H2BHNCHNC trimers, there is enhancing interplay between the single-electron hydrogen bond and another type of hydrogen bond. Although the covalent interaction in H2BNCH and H2BCNH dimers is also enhanced due to presence of the second NCH (CNH) molecule in H2BNCHNCH and H2BCNHCNH trimers, there exists a negative cooperativity between the covalent interaction and the hydrogen bond. The complexes have been analyzed with natural bond orbital (NBO) and atoms in molecules (AIM) theories.