Theoretical and experimental study of molecular structure and vibrational spectra of N -(2-pyridylmethyl)-2-pyrazinecarboxamide

N-(2-Pyridylmethyl)-2-pyrazinecarboxamide was prepared and its crystal structure was investigated by X-ray analysis. The compound crystallizes in the triclinic space group P[`1]P{\bar 1} with a = 4.262(3), b = 12.117(9), c = 20.840(18) ?, α = 91.802(6), β = 89.834(7), γ = 91.845(6)°, V = 1075.2(16) ?³, Z = 4, and D = 1.323 Mg/m³. The structure was solved by direct method and refined to R = 0.0699 and wR ₂ = 0.1268 by full matrix anisotropic least-squares method. Using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set, the molecular geometry and vibrational frequencies of the title compound has been investigated and compared with experimental ones from experimental studies. The optimized bond lengths obtained by RHF method and bond angles obtained by B3LYP method show better agreement with the experimental values. The vibrations computed of the title compound by the RHF and DFT methods are in good agreement with the observed IR spectra data.     

Theoretical and experimental study of molecular structure and vibrational spectra of <Emphasis Type="Italic">N</Emphasis>-(2-pyridylmethyl)-2-pyrazinecarboxamide

N-(2-Pyridylmethyl)-2-pyrazinecarboxamide was prepared and its crystal structure was investigated by X-ray analysis. The compound crystallizes in the triclinic space group \(P{\bar 1}\) with a = 4.262(3), b = 12.117(9), c = 20.840(18) Å, α = 91.802(6), β = 89.834(7), γ = 91.845(6)°, V = 1075.2(16) ų, Z = 4, and D = 1.323?Mg/m³. The structure was solved by direct method and refined to R = 0.0699 and wR ₂ = 0.1268 by full matrix anisotropic least-squares method. Using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set, the molecular geometry and vibrational frequencies of the title compound has been investigated and compared with experimental ones from experimental studies. The optimized bond lengths obtained by RHF method and bond angles obtained by B3LYP method show better agreement with the experimental values. The vibrations computed of the title compound by the RHF and DFT methods are in good agreement with the observed IR spectra data.     

Resonance structure counts in parallelogram-like benzenoids with holes

If a hexacyclic graph G represents a benzenoid, a perfect matching corresponds to a configuration of π-bonds. We present an algorithm for counting the number of configurations of π-bonds for parallelogram-like benzenoids with parallelogram-like holes by counting descending paths in a corresponding rectangular mesh with rectangular holes.     

A combinatorial/geometric analysis of parallelogram-like benzenoids

We recently reported an algorithm to count Kekulé (resonance) structures for convex cyclofusenes using a combinatorial/geometric approach. Previously, we presented an algorithm for counting resonance structures for parallelogram-like benzenoids with holes by counting descending paths using rectangular meshes with holes. In this article, we employ a similar combinatorial/geometric approach to determine algorithms that will facilitate counting of the resonance structures in parallelogram-like benzenoids with no holes.