No abstract

In this work we use Raman spectroscopy and quantum first-principles calculations to unveil the experimental spectrum of a complex molecular solid like benzylic amide [2]catenane, a representative example of a mechanically interlocked molecular architecture. We use large-scale Density Functional Theory calculations to obtain the complete set of vibrational normal modes of the catenane crystal, whose unit cell contains 544 atoms. Subsequently, we demonstrate that these calculations are able to accurately reproduce the experimental Raman spectrum of this molecular compound, without introducing any empirical corrections or fittings i n t he c alculated e igenfrequencies. Thanks to the good agreement between the experimental and theoretical spectra it is possible to carry out the complete assignment of the main vibrational modes responsible for the whole spectrum. A detailed description in terms of the usual internal coordinates is given for all these representative modes. This description, rather difficult from the experimental point of view, provides valuable information about the molecular structure of this compound, compatible with experimental evidences reported in the literature.

In this work we record and assign the infrared spectrum of benzylic amide [2]catenane, a molecular solid owning mechanical bonds. By means of first-principles calculations we analyze over 1000 normal modes in terms of the usual internal coordinates.

Photodissociation of CH2BrI was investigated in search of unimolecular elimination of BrI via a primary channel using cavity ring-down absorption spectroscopy (CRDS) at 248 nm. The BrI spectra were acquired involving the first three ground vibrational levels corresponding to A3Π1 ← X1Σ+ transition. With the aid of spectral simulation, the BrI rotational lines were assigned. The nascent vibrational populations for v'' = 0, 1, and 2 levels are obtained with a population ratio of 1 : (0.58 ± 0.10) : (0.34 ± 0.05), corresponding to a Boltzmann-like vibrational temperature of 713 ± 49 K. The quantum yield of the ground state BrI elimination reaction is determined to be 0.044 ± 0.014. The CCSD(T)//B3LYP/MIDI! method was employed to explore the potential energy surface for the unimolecular elimination of BrI from CH2BrI.