Evidence of blue-shifting N–H⋯N hydrogen bonding despite elongation of the N–H bond

摘要: In most cases of X–H⋯Y hydrogen bonding (X is an electronegative atom and Y any electron-rich center), the X–H bond gets elongated stretching frequency (νX–H) red-shifted. Relatively fewer blue-shifting H-bonding are also known, where contracts leading to increase in νX–H. Here presented first experimental report N–H⋯N that accompanies N–H length as evident from quantum chemistry computations. Pyrrole N2 have been shown form ‘annealed’ matrix, both doped (pyrrole) dopant (nitrogen) molecules had scope align themselves stable H-bonded clusters. The infrared spectrum annealed matrix shows a blue shift νN–H by 7 cm−1. Computation anharmonic frequencies at MP2/6-31+G(d) level theory reflects observed despite lengthening after H-bond formation.