Zhen-hua Zhou

Research on carbon-carbon coupling reactions of haloaromatic compounds mediated by zerovalent nickel complexes. Preparation of cyclic oligomers of thiophene and benzene and stable anthrylnickel(II) complexes

Abstract Dehalogenative carbon—carbon coupling reactions of 3,4-dibromothiophene, 1,2-dihalobenzenes and 9-bromoanthracene using zerovalent nickel complexes as a dehalogenating reagent produced respectively cyclotetrathiophene, triphenylene and 9,′9-bianthracene in good yields. However, two extremely stable arylnickel(II) complexes, Ni(10-X-9-anthryl)X(PPh3)2 (X = Br,Cl), where the 10-CX bond in the anthryl groups was inert against excess Ni0 complexes, were obtained by oxidative addition of 9,10-di- haloanthracenes to the Ni0 complexes. Under similar reaction conditions9,10-dihaloanthracenes did not undergo carbon—carbon coupling reactions.

Unique optical and electrochemical properties of π-conjugated electrically conducting copolymers consisting of electron-withdrawing pyridine units and electron-donating thiophene units

Electrically conducting π-conjugated copolymers consisting of π-excessive thiophene-2,5-diyl and π-deficient pyridine-2,5-diyl monomer units show a unique cyclic voltammogram with an unusually large potential difference between the doping and the undoping peaks, and their electronic and fluorescence spectra support occurrence of intramolecular charge transfer showing absorption and fluorescence peaks at lower energy compared with those of the corresponding homopolymers.

New method using nickel (0) complex for preparation of poly(p-phenylene), poly(2,5-thienylene) and related π-conjugated polymers

Abstract Dehalogenation polycondensation of dihaloorganic compounds with zerovalent nickel complex afforded π-conjugated polymers such as poly(p-phenylene) (PPP) and poly(2,5-thienylene) (PTh) (n X-Ar-X+n Ni (0) Lm → (Ar)n + n NiX2Lm) in good yields. PPP and PTh had high crystallinity and doping of powdery PTh with iodine afforded a material with electrical conductivity of 8 S cm−1. Poly(3-hexyl-2,5-thienylene) had degree of polymerization of ca. 500.

Orientation of linear π-conjugated poly(p-phenylene), poly(thiophene-2, 5-diyl) and poly(2, 2′-bipyridine-5, 5′-diyl) perpendicularly to the surface of carbon and metal substrates. Factors controlling the orientation.

Abstract Vacuum evaporation of π-conjugated poly(p-phenylene), poly(thiophene-2, 5-diyl) and poly(2, 2′-bipyridine-5, 5′-diyl) on carbon substrates affords highly oriented crystalline thin films of the polymer with the polymer chain perpendicular to the surface of the substrates. Electron diffractometory reveals that the order of the orientation of the thin film is affected by substrate temperature, strength of interaction between the polymer molecules and the substrates, and linearity of the polymer molecules.

Electrical and optical properties of poly(2,5-pyridinedyl) and poly(2,2′-bipyridine-5,5′-diyl) prepared by dehalogenation polycondensation using zero-valent nickel-complexes

Abstract Poly(2,5-pyridinediyl) (PPy) and poly(2,2′-bipyridine-5,5′-diyl) (PBpy) composed of inherently π-deficient pyridine rings are soluble in formic acid, show large degree of depolarization ( ϱ v = 0.33) in formic acid, and show fluorescence. n-Type doping of PPy and PBpy (chemically with sodium as well as electrochemically) affords electrically conducting materials, whereas the polymers are essentially inactive against p-type doping.

Properties and structure of substituted poly(thiophene-2,5-diyl), poly(pyridine-2,5-diyl), and their analogues prepared by organometallic processes

Abstract Substituted poly(thiophene-2,5-diyl)s and poly(pyridine-2,5-diyl)s have been prepared by dehalogenative polycondensation of the corresponding dihaloaromatic compounds with zerovalent nickel coplexes. IR spectra of poly(3-alkylthiophene-2,5-diyl)s and poly(3-alkoxythiophene-2,5-diyl)s are essentially the same as those of the corresponding polymers prepared by chemical and electrochemical oxidation, and the polymers show high thermal stability. Poly(pyridine-2,5-diyl) PPy, poly(methylpyridine-2,5-diyl)s PMePys, poly(2,2′-bipyridine-5,5′diyl) PBpy, and poly(quinolinediyl)s PQs have the molecular weight ranging from 3200 to 82000. These polymers are easily converted into n-type conductors by electrochemical as well as chemical reduction. PPy and PBpy takes rigidly linear structure both in solutions and in the solid state, and strong dichroism is observed for stretched poly(vinyl alcohol)-PPy and -PBpy films.

Unique optical and doping behavior of π-conjugated polymers constituted of electron-accepting pyridine and electron-donating thiophene units

Abstract Electrically conducting π-conjugated heteroaromatic copolymers poly(pyridine-5,2-diyl-thiophene-2,5-diyl) PTpy and its analogues have been synthesized in high yields by dehalogenation polycondensation of the corresponding dihaloaromatic compounds with zerovalent nickel complex. PTpy has Mw of 5400 and [η] of 2.26 dL g −1 . The polymers are soluble in formic acid, and their electronic as well as fluorescence spectra give rise to visible and fluorescence peaks whose positions indicate occurrence of intramolecular charge transfer in the polymer molecules. They show unique cyclic voltammograms with unusually large potential difference between the p-doping (0.4 V vs Ag/Ag + ) and p-undoping peaks (−1.7 V), which is accounted for by an EC mechanism. Random copolymers of pyridine-2,5-diyl and thiophene-2,5-diyl show similar unique optical and electrochemical behaviors.

Third-order nonlinear optical properties of processible polymeric materials

Third-order nonlinear optical properties, (chi) (3), of novel polymeric materials having large (chi) (3) with processabilities are discussed. These polymers reported here have a potential to fabricate optical switching devices.