Chemistry at Low Pressure and Low Temperature: Rotational Spectrum and Dynamics of Pyrimidine-Neon

Abstract

The equilibrium configuration, dynamics, and dissociation energy of the very weakly bonded pyrimidine´´´Ne complex have been deduced from its free jet millimeter wave spectrum. The equilibrium distance of Ne with respect to the center of mass of the molecule is 3.27 , with Ne tilted 5.18 from the perpendicular to the center of mass of the ring toward the mid-point of the two nitrogen atoms. The dissociation energy is estimated, from the centrifugal distortion constant D J , to be about 1.3 kJ mol À1.

Fourier transform microwave spectrum of pyridine–neon

“…Generally the RG stretching motion has been considered isolated from the bending motions, and its frequency has been obtained from the D J centrifugal distortion constant within a pseudo-diatomic approximation. From these frequencies, approximate values of dissociation energies have been obtained [8][9][10][11][12][13]. Also information on the bending motions has been obtained, either from centrifugal distortion constants [14], or from mass distribution and Coriolis effects [12].…”

“…Also in the case of pyridine, the rotational spectra of four pyridine-RG adducts have been measured, with FTMW spectroscopy for RG = He [5], Ar [6,7] and Kr [6], and with free jets mmw spectroscopy for RG = Ne [8] and Ar [9]. In addition, the free jets mmw spectra of pyrimidine-Ne [10], pyridazine-Ne [11] pyrimidine-Ar [12] and pyridazine-Ar [13] have been reported.…”

Rotational spectrum, dynamics, and bond energy of the floppy dimethylether⋯neon van der Waals complex

“…In the case of 5 or 6 membered aromatic ͑or nearly aromatic͒ rings the Ne atom was localized on one side of the ring and no tunneling effects were observed. [5][6][7][8][9] In the above mentioned case of 1,1-difluoroethylene-Ne 3 a small splitting in the rotational transitions allowed for the determination of the barrier to the Ne inversion. In some other cases, such as ethylene oxide-Ne and difluoromethane-Ne, 10 huge splittings ͑of the order of several GHz͒ have been measured, but it was very difficult to fit the lines of both states all together.…”

Rotational spectra and dynamics of the van der Waals adducts of neon and argon with 1,1-difluoroethylene

“…This ratio ͑Х0.5͒ is larger than those observed for complexes of Ne and Ar with cyclic molecules, were the dissociation energies for the neon adducts 3-4 times smaller than that of argon adducts. [19][20][21] It seems that the higher number of interaction centers in cyclic molecule is more effective in increasing the stabilization energy for Ar, rather than for the Ne complexes.…”