TOPIC: Benzazoles as Broad-Spectrum Fluorescent Sensors and Components of Self-Organizing Systems

GUEST SPEAKER:  Assistant Professor Ognjen S. Miljanic

INSTITUTE: Department of Chemistry, University of Houston

Date: Sunday, February 5th, 2012

Time: 11:00 – 12:00 noon

Location: Ibn Al-Haytham Building, (Bldg 2), Level 5, # 520

 

Abstract:

This seminar will present the recent work in the Miljanic research group at the University of Houston. The first part of the presentation will discuss the synthesis, characterization, and sensing properties of cruciform-shaped fluorophores based on the benzobisoxazole nucleus. In these molecules, donor-acceptor substitution enforces strict localization of HOMO along one of the cruciforms' "arms" and LUMO along the other. This spatial separation of orbitals is essential to their sensing behavior, as analyte binding to any part of the cruciform invariably alters the HOMO-LUMO gap and the associated optical properties. This class of molecules has been used to discriminate among structurally closely related carboxylic and boronic acids.

In addition, a hybrid system composed of our cruciform fluorophores and boronic acids is able to sense a wide variety of Lewis bases, including many common anions, amines, ureas, etc. The second half of the talk will focus on the self-sorting behavior which can be observed in the synthesis of some benzoxazole and benzimidazole systems. In this protocol, a very complicated mixture of precursors is induced to express individual components in high yields and purities. This represents a significant parallel to the way Nature targets the synthesis of complex organic compounds--without any protecting groups or purification steps.