A theoretical systematic study of a series of isocyanopolyynes

摘要: Abstract Several isocyanopolyynes, HC n NC (  = 0, 2, …, 16), are analyzed in this theoretical work. We performed calculations at MP2/cc-pVTZ  = 0–16), CCSD/cc-pVDZ  = 0–12) and CCSD/cc-pVTZ  = 0–6) levels. The dipole moments from the best treatment, CCSD/cc-pVTZ, much closer agreement with those obtained (deviations up to 0.05 Debye) than results (discrepancies that can reach 0.55 Debye). Moreover, level yields values excellent accordance experimental for HNC 2 NC. Hence, allows concluding correct treatment of electron correlation is more important increments basis sets electric property isocyanopolyynes indicated as estimates available large isocyanopolyynes. findings infrared intensities fundamental vibrational bands also similar (mean deviations 3.1 km mol −1 12.6 km mol respect results). Thus, we decided use charge – flux (CCFDF) model multipoles given by Quantum Theory Atoms Molecules (QTAIM), which were level, investigate variations some selected modes along these systems. intensity band associated CH stretching shows an increase size molecules (from 96 146 km mol between  = 4 12) readily explained contribution mode, a way found before cyanopolyynes. Furthermore, degenerate bending vibrations present almost constant (around 37–38 km mol  = 12) pattern supported CCFDF/QTAIM contributions. mostly assigned triple bond, be described asymmetric mode all pairs adjacent bonds,  = 6 around 96–102 km mol remaining larger members. Another detected symmetric CC bonds belonging isonitrile end (between 66 101 km mol when  = 6–12) nearly dynamic contributions change complicated way. most intense each isocyanopolyyne 12 both ends systems 129 164 km mol ) alternating behavior according even or odd numbers observed respective Finally, work brings derived regressions rotational constants used detection interstellar medium.