Photochromism Control of Salicylideneaniline Derivatives by Acid–Base Co-Crystallization

Abstract

Acid–base co-crystallization has been used to control the photochromic reactivities of salicylideneaniline derivatives in co-crystals. The series of co-crystals N-salicylidene-3-carboxyaniline (1) with 2-aminopyridine (a), guanylthiourea (b), cytosine (c), 4,4′-bipyridyl (d), piperazine anhydrous (e), 1,3-di-o-tolylguanidine (f), and dibenzylamine (g) and N-salicylidene-4-carboxyaniline (2) with 4,4′-bipyridine (d) and N,N-dibenzylamine (g) have been synthesized. The weak photochromic compound 1 becomes nonphotochromic or strongly photochromic in the co-crystals and the nonphotochromic compound 2 becomes photochromic in the co-crystal 2g. The photochromic properties of compounds 1 and 2 change because of the conformational changes induced in the salicylideneaniline moieties in the crystal structure. The lifetimes of the colored species formed in the photochromic reaction are also affected by the changes in the environment around the molecule in the crystal. As shown in this study, acid–base type co-crystallization may be a promising method to control the photochromic reactivities of salicylideneaniline derivatives.

Structure and Photochemistry of N-Salicylidene-p-carboxyaniline Isolated in Solid Argon

“…The preferred geometry about the NC bond can be expected to have the salicylidene−azomethine and p-carboxyphenyl fragments in different planes, taking as reference what has been found for other molecules bearing similar structural elements. 28,29 Considering points (i)−(iv) above, it can be concluded that the number of relevant structures for each enol isomer (E and Z forms, which are defined by the orientation of the groups around the CN bond) is in fact rather small.…”

Halogen‐Bond Effects on the Thermo‐ and Photochromic Behaviour of Anil‐Based Molecular Co‐crystals

“…Whereas photochemical back reactions are characterised by bi‐exponential behaviour, the thermal fading processes are well described by first‐order reactions. A two‐stage thermal decay of the trans ‐keto form of anils in the solid state has been previously reported . It can be observed that the two co‐crystals show much faster back reactions than that of simple compound 2 : the photoconversion kinetics of the trans ‐keto tautomer are of the order of tens of seconds for 2 2 ⋅I2F4 and 3 2 ⋅I2F4 and tens of minutes for 2 (Figures S17–S19 in the Supporting Information).…”

“…At wo-stage thermal decay of the trans-keto form of anils in the solid state has been previously reported. [9,12,13,62] It can be observed that the two co-crystals show much faster back reactions than that of simple compound 2:t he photoconversion kinetics of the trans-keto tautomer are of the order of tens of seconds for 2 2 ·I2F4 and 3 2 ·I2F4 and tens of minutes for 2 (Figures S17-S19 in the SupportingI nformation). Concerning thermalf ading, conversion times of 604, 65 and 186 min have been measured for the trans-keto form of 2, 2 2 ·I2F4 and 3 2 ·I2F4,r espectively; this confirms that 2 undergoes the slowest process.…”

A biomimetic fluorescent chemosensor for highly sensitive zinc(ii) detection and its application for cell imaging

“…To this end, several elegant strategies have been developed to overcome the aws of small molecule probes, for example conjugating or loading them into inorganic nanoparticles, micelles, polymers, and so forth. [38][39][40][41][42][43] Of all of the above, polymer-based uorescent chemosensors have several advantages over the others, such as water solubility, exceptional processability, and signal amplication. Hence, efforts have been dedicated to the fabrication of polymeric chemosensors, which contain salicylaldimine Schiff bases.…”