Zhikuan Lu

Copper-catalyzed amination of aromatic halides with 2-N, N-dimethylaminoethanol as solvent

A copper-catalyzed amination of aromatic halides under mild conditions using N,N-dimethylaminoethanol as solvent is described. We have studied this reaction in some detail varying the copper source, base, water content and other parameters including the scope of useful amine and aromatic halide structures. A variety of 4-halo-N,N-cycloalkylanilines and 2-N,N-cycloalkylaminothiophenes were synthesized for further elaboration into chromophores for optoelectronic applications.

Solvent effects on the nonlinear optical response of a potentiometric biological imaging dye

To understand the electronic mechanisms for the electric-field sensitive second-harmonic response of di-8-4-(2-[6-(dioctylamino)-2-naphthalenyl]ethneyl)-1-(3-sulfopropyl) pryridinium inner salt in biological membranes, we have measured its nonlinear optical hyperpolarizability using a combination of hyper-Rayleigh scattering and linear optical properties in solvent environments of various polarity. Changes in the first hyperpolarizabilities are discussed by modeling experimental inputs from the solvatochromic effect in linear absorption and appropriate dispersion relations near the two-photon resonance. We find that both frequency-dependent and frequency-independent effects make significant contributions to the response, and the strongest response is on the low-energy side of the two-photon resonance, while the weakest response is on the high-energy side of the two-photon resonance.

Single crystal, liquid crystal, and hybrid organic semiconductors

The synthesis and characterization of organic semiconductors is being pursued in three primary structure formats: single crystal, liquid crystal and organic-inorganic hybrid. The strategy here is to share common structures, synthesis methods and fabrication techniques across these formats and to utilize common characterization tools such as the time of flight technique. The single crystal efforts concentrate on aromatic and heteroaromatic compounds including simple benzene derivatives and derivatives of the acenes. The structure-property relationships due to incorporation of small substituents and heteroatoms are being examined. Crystals are grown by solution, melt or vapor transport techniques. The liquid crystal studies exploit their self-organizing properties and relative ease of sample preparation. Though calamitic systems tha deliver the largest mobilities are higher order smectics, even some unusual twist grain boundary phases are being studied. We are attempting to synthesize discotic acene derivatives with appropriate substitution patterns to render them mesogenic. The last format being examined is the hybrid organic-inorganic class. Here, layered materials of alternating organic and inorganic composition are designed and synthesized. Typical materials are conjugated aromatic compounds, usually functinalized with an amine or a pyridine and reacted with appropriate reactive metal derivatives to incorporate them into metal oxide or sulfide layers.