Synthesis and X-ray Crystal Structure of New Substituted 3-4′-Bipyrazole Derivatives. Hirshfeld Analysis, DFT and NBO Studies

A new compounds named 3-4′-bipyrazoles 2 and 3 were synthesized in high chemical yield from a reaction of pyran-2,4-diketone 1 with aryl hydrazines under thermal conditions in MeOH. Compound 2 was unambiguously confirmed by single-crystal X-ray analysis. It crystalizes in a triclinic crystal system and space group P-1. Its crystal structure was found to be in good agreement with the spectral characterizations. With the aid of Hirshfeld calculations, the H…H (54.8–55.3%) and H…C (28.3–29.2%) intermolecular contacts are the most dominant, while the O…H (5.8–6.5%), N…H (3.8–4.6%) and C…C (3.0–4.9%) are less dominant. The compound has a polar nature with a net dipole moment of 6.388 Debye. The BD(2)C31-C32→BD*(2)N4-C34 (27.10 kcal/mol), LP(1)N5→BD*(2)C31-C32 (36.90 kcal/mol), BD(1)C32-C34→BD*(1)C18-C31 (6.78 kcal/mol) and LP(1)N4→BD*(1)N5-C31 (7.25 kcal/mol) are the strongest π→π*, n→π*, σ-σ* and n→σ* intramolecular charge transfer processes, respectively.