Study of Model Systems for Bilirubin and Bilin Chromophores: Determination and Modification of Thermal and Photochemical Properties

Bilin
chromophores and bilirubin are involved in relevant biological
functions such as light perception in plants and as protective agents
against Alzheimer and other diseases. Despite their extensive use,
a deep rationalization of the main factors controlling the thermal
and photochemical properties has not been performed yet, which in
turn hampers further applications of these versatile molecules. In
an effort to understand those factors and allow control of the relevant
properties, a combined experimental and computational study has been
carried out for diverse model systems to understand the interconversion
between Z and E isomers. In this
study, we have demonstrated the crucial role of steric hindrance and
hydrogen-bond interactions in thermal stability and the ability to
control them by designing novel compounds. We also determined several
photochemical properties and studied the photodynamics of two model
systems in more detail, observing a fast relaxation of the excited
state shorter than 2 ps in both cases. Finally, the computational
study allowed us to rationalize the experimental evidence.