Structure–property relationships in normal and mixed dithienylethenes – polyoxometalates supramolecular assemblies with fast solid-state photochromic properties. Issue 3 (7th December 2021)

• Record Type: Journal Article
• Authors: Stetsiuk, Oleh; Bolle, Patricia; Cordier, Marie; Boixel, Julien; Dessapt, Rémi
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 3(2022)
• Page Start: 899
• Page End: 907
• Publication Date: 2021-12-07
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d1tc04561j
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : A strategy of sequential modification of organic and inorganic components gave rise to a stepwise photophysical investigation of the photochromic performances of supramolecular assemblies of polyoxometalates with normal or mixed dithienylethenes. Abstract : Five new highly photochromic hybrid organic–inorganic materials were successfully prepared by supramolecular assembly of normal (1 + ) and mixed (2 + ) cationic dithienylethenes (DTEs) and polyoxometalates (POMs) units. Single-crystal X-ray diffraction studies reveal that (1)3 [PM12 O40 ]·5ACN (M = W, Mo) (1-PW12 and 1-PMo12 ) and (2)3 [PM12 O40 ]·5ACN (M = W, Mo) (2-PW12 and 2-PMo12 ) are isostructural, while (2)4 [Mo8 O26 ]·4DMF (2-Mo8 ) is an isotype of (1)4 [Mo8 O26 ]·4DMF (1-Mo8 ) i.e., the first POM–DTE ionic assembly, recently reported. The solid-state photochromic properties of these materials at room temperature are highly tunable with the nature of the DTEs and POMs used, which has been interpreted taking into account steric and electronic factors. Especially, while 1-PMo12 and 2-PMo12 exhibit negligible photoresponses which have not been considered herein, thorough investigations of the photocoloration and fading kinetics in ambient conditions have highlighted the precise impact of both organic and inorganic components on the photoswitching abilities of 1-Mo8, 2-Mo8, 1-PW12 and 2-PW12 . Upon UV-light irradiation, the absorption of the normal and mixed DTEs in their closed-ring form exhibits a hypsochromic shift which is more pronounced in hybrid systems integrating β-[Mo8 O26 ] 4− rather than α-[PW12 O40 ] 3−, due to the higher negative charge density of the octamolybdate unit. The photocyclization rates of DTEs are also systematically increased when combined with the β-[Mo8 O26 ] 4− unit, while in contrast, their back cycloreversion rates are not affected whatever the nature of the POMs used. In addition, within isostructural series, hybrids integrating mixed DTEs exhibit faster fading processes than their normal DTE counterparts when exposed to visible light. Finally, among this new series, 2-Mo8 shows the best photochromic performances with a fast photocoloration rate associated with a high coloration contrast, a fast and complete fading process and a high cyclability.