Multitask molecular springs: Collective helical vibrations of R2Sn (R = H, C6H5, C2H3, CCl3) - A quantum mechanical study
(EN)
Papamokos, G. V.
(EN)
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
(EL)
Papamokos, G. V.
(EN)
The H2Sn homologous series is proposed as a model for the collective vibrations of helical molecules. The polysulfane series was selected as the molecular set that resembles most closely a molecular discretization of a continuous helical curve. The computational vibration analysis for the levels of theory-MNDO, RHF/3-21G, RHF/6-31G*, RHF/6-31G**, MP2(FC)/6-31G*, and DFT B3LYP/6-31G*-revealed a number of collective vibrations. These vibrations resemble the motion of (a) a transverse wave, (b) a longitudinal wave, and (c) a transformation of the cylindrical shape to a breathing pulse, to an ellipsoidal-hyperboloidal, or to a cone. The precursor of a helical transverse wave is SSSS torsional vibrations, while SSS bending vibrations are the precursor of a longitudinal wave; finally, aggregated SS stretching is the precursor and generative force for the reported changes of the cylindrical helical shape (breathing, conical, ellipsoidal-hyperboloidal). The number of sulfur atoms and the hydrogen substitution were studied for their effects on appearance/disappearance of the characteristic helical vibrations. Also, they were studied for their effects on the overall molecular shape. The helical structure of polysulfanes is proposed to be ideally suited to provide a reference molecular prototype for classification of the low-frequency vibrations of helical biopolymers leading to global bend, global stretch, or breathing, conical, ellipsoidal-hyperboloidal transformations. Vibrations of this kind are particularly interesting for their biological and nanomechanical functions.
(EN)
