Theoretical Aspects of Werner Complexes and Molecular Devices

Abstract

This dissertation begins with the first comprehensive review of molecular gyroscopes. The following two chapters feature combined experimental/computational studies. In the first, equilibria involving gyroscope-like complexes and geometric isomers are measured and the data interpreted with molecular dynamics simulations and DFT calculations. In the second, trigonal bipyramidal diiron tetraphosphorus complexes that have parallel P–Fe–P axes and the potential for coupled Fe(CO)3 rotators are examined. Here the DFT studies focus mainly on electronic structure and IR properties.

The rotators can be removed from the gyroscope-like complexes to give unprecedented dibridgehead diphosphines with long (CH2)n linkers. Their conformational, dynamic, and NMR properties are interrogated by simulated annealing and DFT calculations, helping to rationalize observed behavior and predicting properties of molecules that remain to be synthesized.

Another major class of molecules investigated is polyynes H(C≡C)n'H which are of special interest at long chain lengths (models for the polymeric sp carbon allotrope carbyne). Nucleus independent chemical shifts are revealing an absence of special shielding regions and DFT calculations provide highly accurate chemical shift values, including polyynes with platinum endgroups. Complexes with four platinum corners and four –(C≡C)2– edges can be accessed. Electrostatic potential maps show highly negatively charged cores that explain the strong affinities of these species for ammonium salts. DFT calculations also establish very similar energies for planar vs. puckered conformations, both of which have been observed crystallographically: electronic structures and equilibria involving Pt3 and Pt5 homologs are also thoroughly explored.

Werner complexes of the type [Co(en)3]3+ 3X– (en = 1,2-ethylenediamine) have also been extensively investigated. In one study, the intricate stereochemical and conformation properties are reviewed including substituted derivatives using conventions from both organic and inorganic chemistry. In another, >150 crystal structures of [Co(en)3]3+ salts have been analyzed with respect to hydrogen bonding between the NH groups and the counteranions. Diverse motifs could be identified and a nomenclature syntax developed.