Pseudo crystalline state thermochromic and reverse-photochromic reactivity of spiroindolinobenzopyran upon encapsulation into Zn-MOF-74

Abstract

Drastic changes observed in chromic properties of an unsubstituted spiroindolinobenzopyran encapsulated into a MOF lattice are reported.

Negatively photochromic organic compounds: Exploring the dark side

“…89 Solvent dependent negative photochromism was also noted for mononitrospiropyrans derived from 5-amino Fischer's base with the mononitrospiropyran -Schiff base dyad 16 90 and supramolecular hydrogels based on mononitrospiropyranpeptide conjugates 17 (Figure 8). 91 The matrix also has a significant impact on the routine photochromic switching of the parent spiropyran 1 which can be modified to exhibit negative photochromism when it is entrapped in the rigid channels of a zinc ion-rich metal organic framework 92 and covalent linking of 6-hydroxyspyropran to the polymer backbone of an acrylate copolymer stabilised the coloured zwitterionic form which could be reversibly bleached upon irradiation. 93 Temporary negative photochromism was imparted into two long chain substituted mononitrospiropyrans 18 and 19, in thin films, upon protonation with HCl.…”

A steric hindrance alleviation strategy to enhance the photo-switching efficiency of azobenzene functionalized metal–organic frameworks toward tailorable carbon dioxide capture

“…10 Therefore, photo-responsive MOFs have been developed to overcome this challenge by triggering the release of CO 2 under abundant and renewable light. [11][12][13] Considering the high degree of structural tunability of MOFs, the integration of photochromic units such as azobenzene, 14 diarylethene 15 and spiropyran 16 into MOFs as pendant groups, 17 backbones 18 or guest molecules 19 has been reported to confer photo-switching features to MOFs. Particularly, azobenzene is among the most popular candidates for switching units, not only because of its versatile and simple integration approach, 20 but also owing to its capability of providing alternative CO 2 capture sites.…”

Modulating the Optical Characteristics of Spiropyran@Metal–Organic Framework Composites as a Function of Spiropyran Substitution

“…It is precisely in these points, however, that the inserted dyes experience a high degree of mobility, which allows studying preferred interaction sites within the MOF scaffold. Various photochromic molecules were implemented in this respect: stilbenes, azobenzenes and derivatives, ,− 2-phenyl-(azopyridines), , spiropyrans, ,− spirooxazines, diarylethenes, , and anthracenes . The resulting hybrid materials have been comprehensively studied regarding their optical properties originating from the host framework, as well as their potential applications.…”