HCN Clusters in Molecular Beams and Cryogenic Matrices

Abstract

Cluster formation of hydrogen cyanide (HCN) was traced by mass spectroscopy in molecular beams and by FTIR spectroscopy in cryogenic matrices in which the clusters were embedded. Both experiments provided evidence for the presence of linear (n ≥ 2) and cyclic structures (n ≥ 3) which were predicted by ab initio calculations as comparably stable. The mass spectra clearly reflect a fundamentally different behaviour of the two types of clusters within the expansion zone: the linear species exhibit the cabability of cluster growth, while the cyclic ones do not. This leads to a characteristic size distribution with two marked maxima. During matrix deposition, considerable distortions of the clusters are created which may be healed out by annealing. The resulting sharp bands in the CH stretching region were assigned in agreement with ab initio calculations and previous IR studies aiming at small linear and cyclic species (n ≤ 3) in diverse liquid and solid environments.

Solvent mediated vibrational relaxation: Superfluid helium droplet spectroscopy of HCN dimer

“…While rotational resolution is available in both the microwave 8,9 and infrared [13][14][15][16] gas phase studies, the broadening associated with the inhomogeneous environment in a cold, solid matrix results in broad vibrational bands that mask the dynamics. 24,25 It is clear from all of this work that the preferred structure of the dimer is linear, with the one HCN hydrogen bonded to the other. As with many other weakly bound complexes, the hydrogen bond is quite floppy in this system.…”

Salts of HCN‐Cyanide Aggregates: [CN(HCN)2]− and [CN(HCN)3]−

“…In fact, this effect can be considered secondary, since the arrangement of the bulky cations seems to be the primary effect responsible for the size of the cavities, in which the anions are located. For comparison, structural studies of HCN also indicated that HCN forms linear hydrogen‐bonded aggregates in all its phases . For example, there are infinite, parallel, linear H‐bridged chains in HCN crystals .…”

A Dimer of Hydrogen Cyanide Stabilized by a Lewis Acid

“…on the primitive earth, thus playing an important role in prebiotic synthesis. [8][9][10][11][12][15][16][17] With respect to the latter,c ondensation products of HCN are thought to be key intermediates.H ence,aplethora of theoretical [18][19][20][21][22][23][24][25] and experimental [16,19,20,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] studies have been performed on HCN and its clusters (HCN) n in the gas phase (microwave rotational spectroscopy,I R, or matrix IR). These studies indicated that HCN forms linear H-bonded clusters in all its phases.Crystal structure elucidation revealed "infinite" parallel, linear hydrogen-bonded chains, [41] while for the liquid phases, al inear structure with an association state of n = 3w as experimentally derived.…”