Raman, infrared and NMR spectra, vibrational assignments and quantum mechanical calculations of centrosymmetric 3,6-Dicholoro-1,2,4,5-tetrazine

摘要

The Raman spectrum (2000-100 cm(-1)) of 3,6-Dicholoro-1,2,4,5-tetrazine (DCTZ, C2N4Cl2) in solid phase has been recorded. Moreover, the mid-IR (2000-400 cm(-1)) and ATR-IR (2000-480 cm(-1)),C-13 (0-200 ppm) and N-15(0-440 ppm) NMR spectra were recorded. Initially, optimization followed by frequency calculations were carried out for DCTZ restricted to C-i and D-2h point groups to work out the least energy conformer with real frequencies. DET(B3LYP) and MP2(full) computations utilizing 6-31G(d) and 6-311++G(d,p) basis sets favor Ci symmetry conformer by 781/598 cm(-1) (9.3/7.2 kjmol(-1)) and 745/698 cm(-1) (8.9/83 kjmol(-1)). The simulated spectra are well compiled to the experimentally recorded IR, Raman, C-13 and N-15 regardless of few coincident vibrational frequencies that belong to D2h symmetry conformer. Thus, we have carried out additional CASTEP solid state optimization for one molecule per unit cell (C-i symmetry) employing Materials Studio using DFT-PBE method. Similar calculations were completed for D(2)h molecular symmetry for one molecule and repeated molecules per unit cell in which C-i symmetry is favored by 341 cm(-1)(4.1 kjmol(-1)). It is worth mentioning that computations for both C-i and D-2h conformers produce real vibrational frequencies. Assisted by normal coordinate analysis, potential energy distributions (PEDs), complete and confident vibrational assignments are provided herein for C-i conformer. The results are conferred herein are compared with comparable molecules whenever applicable. (C) 2018 Elsevier B.V. All rights reserved.