Supersonic jet spectroscopy of synthetic foldamers, multichromophores, and their water containing clusters

A central theme specific to this dissertation concerns the conformation-specific spectroscopy of flexible molecules in an effort to bridge the complexity gap. Generally, molecules in the complexity gap have several flexible coordinates yet conformational isomerization still occurs along a simple reaction coordinate on the potential energy surface. Molecules in this regime benefit greatly from experiments probing the potential energy surfaces and provide a means to develop and test new theories in an effort to explain more complex system. These measurements are possible through the utilization of a supersonic jet expansion to collisionally cool molecules into their vibrational zero-point levels, collapsing the distribution of conformational isomers to the lowest-energy minima on the potential energy surface. This collisional cooling afforded by the expansion allows researchers to study transient species, molecular cluters, radicals and ions in a conformation-specific fashion. Overall, this dissertation contains three sets of molecules in an effort to bridge the complexity gap: synthetic foldamers, multichromophores, and water containing complexes. For the synthetic foldamers, a set of 21 conformations that represent the full range of H-bonded structures were chosen to characterize the conformational dependence of the vibrational frequencies and infrared intensities of the local amide I and amide II modes and their amide I/I and amide II/II coupling constants. These amide I/I and amide II/II coupling constants remain similar in size for α-, β-, and γ-peptides despite the increasing number of C-C bonds separating the amide groups. These findings provide a simple, unifying picture for future attempts to base the calculation of both nearest-neighbor and next-nearest-neighbor coupling constants on a joint footing There are numerous circumstances of fundamental importance in which two or more ultraviolet chromophores are in close proximity, influencing the intrinsic properties of the close lying, vibronically coupled excited states. Whether incorporated in the same molecule or present as separate monomers, the excited state properties depend on the distance, relative orientation, and strength of the electronic coupling between the two chromophores. Our focus here is then the conformational dependent vibronic coupling observed between ultraviolet chromophores, and the effects of adding a single water molecule or network of water molecules on the vibronic coupling