Photobehaviour of Z‐1,2‐di‐(3^′‐methoxynaphth‐2^′‐yl)ethene as model compound of biphotochromic supermolecules with Z‐ethenic bridge

Abstract

Abstract. This work is part of a research project aimed at investigating the behaviour of biphotochromic supermolecules where two photochromic units of the spirooxazine or chromene series are linked through a conjugated or unconjugated spacer. Preliminary investigations showed that the compounds with ethane, acetylene or ester bridges behave as classical photochromes while those with an ethene bridge showed good coloration accompanied by unusual thermal irreversibility at room temperature. The temperature effect on the spectral behaviour allowed such irreversibility to be explained by the occurrence of a cyclization process at the central ethene bond, typical of Z-diarylethenes. To better understand this photobehaviour, a deep investigation of a model molecule, Z-1,2-di-(3'-methoxynaphth-2'-yl)ethene, was carried out. This paper reports the results obtained on the model molecule and two biphotochromic systems containing benzochromene and spirooxazine units.

Bistable and Multistable Systems

“…In a systematic investigation, several biphotochromic supermolecules have been synthesized in which two photochromic units of the spirooxazine and chromene families are linked through a conjugated or unconjugated spacer [98][99][100]. The colors of spirooxazine and chromene are in the 600 and 450 nm regions, respectively; in compounds containing both spirooxazine and chromene units, therefore, it might be expected that the color can be tuned.…”

“…Some of the compounds examined are shown in Figure 8.12. In these systems, the reactivity of the central double bond [100] competes with the reactivity of the photochromic units and leads irreversibly to cyclic compounds. The photochemical and dynamic properties of these compounds are different from those of the single components.…”

Comprehensive Photokinetic and NMR Study of a Biphotochromic Supermolecule Involving Two Naphthopyrans Linked to a Central Thiophene Unit Through Acetylenic Bonds¶

“…The present study was carried out in the framework of a research project on the excited‐state properties of supermolecular structures containing two photochromic moieties linked through different spacers. In previous publications, the properties of compounds where two spirooxazines or chromenes or mixed spirooxazine–chromene units were linked by ethane, ester and acetylene bridges (reversible photochromic systems) or by an ethene bridge (irreversible systems) have been described (3–5). In the last case, the change from irreversible to reversible behavior on decreasing temperature was also investigated (3).…”

Comprehensive Photokinetic and NMR Study of a Biphotochromic Supermolecule Involving Two Naphthopyrans Linked to a Central Thiophene Unit Through Acetylenic Bonds¶

“…The present study was carried out in the framework of a research project on the excited-state properties of supermolecular structures containing two photochromic moieties linked through different spacers. In previous publications, the properties of compounds where two spirooxazines or chromenes or mixed spirooxazinechromene units were linked by ethane, ester and acetylene bridges (reversible photochromic systems) or by an ethene bridge (irreversible systems) have been described (3)(4)(5). In the last case, the change from irreversible to reversible behavior on decreasing temperature was also investigated (3).…”

“…In previous publications, the properties of compounds where two spirooxazines or chromenes or mixed spirooxazinechromene units were linked by ethane, ester and acetylene bridges (reversible photochromic systems) or by an ethene bridge (irreversible systems) have been described (3)(4)(5). In the last case, the change from irreversible to reversible behavior on decreasing temperature was also investigated (3). The number, concentration and structure of the colored photoproducts were unambiguously determined by 1 H-and 19 F-nuclear magnetic resonance (NMR) spectroscopy (6)(7)(8).…”