The structure and characteristics of photochromic dithienylethenes

M M Krayushkin,L G Vorontsova,B M Uzhinov

doi:10.1155/s1110662x01000034

Abstract

The data on X-ray diffraction analysis for dihetarylethenes with perfluorocyclopentene (F), maleic anhydride (M) and cyclobutenedione (S) bridges between thienyl fragments were summarized and their photochromic properties were discussed. It was established that benzoxazole and benzothiazole substituents in position 5 of thienyl rings are coplanar to the plane of thiophene cycles. Thienyl fragments in A form of all dithienylethenes are considerably turned relative to the plane of bridging cycle. It means that there is no conjugation betweenπ-electrons of aromatic heterocycles and double bond of the bridge.Flattening of molecule frameworkand the envelope conformation of thienyl cycles because of aromaticity loss are characteristic features of the form B structure with F-bridge. In all cases (excluding the compounds with alkylthio substituents in position 2 of thiophene cycle) the photochromic transitionA→Bis observed independently of different nature and structure of functional groups.

Highlights

In recent years the photochromic materials have been considered as promising systems for information storage [1, 2]
Fatigue resistance as applied to photochromes is determined as the quantity of cycles of A and B intercoversion at the irradiation corresponding to the decomposition of 20% of the sample [2]
Irie has shown that photochromic dihetarylethenes possess the thermal irreversibility but a high fatigue resistance comprising in some cases thousands cycles

Summary

INTRODUCTION

In recent years the photochromic materials have been considered as promising systems for information storage [1, 2]. Such compounds should fit a variety of requirements. Irie has shown that photochromic dihetarylethenes possess the thermal irreversibility but a high fatigue resistance comprising in some cases thousands cycles. These unique characteristics arise a considerable interest to dihetarylethenes. The objective of the present paper—to summarize the literature data on the crystal and molecular structures of dihetarylethenes having perfluorocyclopentene, maleic anhydride and cyclobutenedione as ethenic bridges between thienyl fragments

PERFLUOROCYCLOPENTENE DERIVATIVES

COOC EtS

THE DERIVATIVES OF CYCLOBUTENEDIONE AND MALEIC ANHYDRIDE

Findings

CONCLUSION