Physicochemical study of spiropyran–terthiophene derivatives: photochemistry and thermodynamics

Abstract

The photochemistry and thermodynamics of two terthiophene (TTh) derivatives bearing benzospiropyran (BSP) moieties, 1-(3,3''-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4''-didecyloxy-2,2':5',2''-terthiophene-30-acetate (BSP-2) and 1-(3,3''-dimethylindoline-6'-nitrobenzospiropyranyl)-2-ethyl 4,4''-didecyloxy-2,2':5',2''-terthiophene-30-carboxylate (BSP-3), differing only by a single methylene spacer unit, have been studied. The kinetics of photogeneration of the equivalent merocyanine (MC) isomers (MC-2 and MC-3, respectively), the isomerisation properties of MC-2 and MC-3, and the thermodynamic parameters have been studied in acetonitrile, and compared to the parent, non-TTh-functionalised, benzospiropyran derivative, BSP-1. Despite the close structural similarity of BSP-2 and BSP-3, their physicochemical properties were found to differ significantly; examples include activation energies (Ea (MC-2) = 75.05 kJ mol -1 , E a(MC-3) = 100.39 kJ mol -1 ) and entropies of activation (DSz MC-2 = 43.38 J K -1 mol -1 , DSz MC-3 = 37.78 J K -1 mol -1 ) for the thermal relaxation from MC to BSP, with the MC-3 value much closer to the unmodified MC-1 value (46.48 J K -1 mol -1 ) for this latter quantity. The thermal relaxation kinetics and solvatochromic behaviour of the derivatives in a range of solvents of differing polarity (ethanol, dichloromethane, acetone, toluene and diethyl ether) are also presented. Differences in the estimated values of these thermodynamic and kinetic parameters are discussed with reference to the molecular structure of the derivatives. The photochemistry and thermodynamics of two terthiophene (TTh) derivatives bearing benzospiropyran (BSP) moieties, 1-(3,3 00 -dimethylindoline-6 0 -nitrobenzospiropyranyl)-2-ethyl 4,4 00 -didecyloxy-2,2 0 :5 0 ,2 00 -terthiophene-3 0 -acetate (BSP-2) and 1-(3,3differing only by a single methylene spacer unit, have been studied. The kinetics of photogeneration of the equivalent merocyanine (MC) isomers (MC-2 and MC-3, respectively), the isomerisation properties of MC-2 and MC-3, and the thermodynamic parameters have been studied in acetonitrile, and compared to the parent, non-TTh-functionalised, benzospiropyran derivative, BSP-1. Despite the close structural similarity of BSP-2 and BSP-3, their physicochemical properties were found to differ significantly; examples include activation energies (E a(MC-2) = 75.05 kJ mol À1 , E a(MC-3) = 100.39 kJ mol À1 ) and entropies of activation) for the thermal relaxation from MC to BSP, with the MC-3 value much closer to the unmodified MC-1 value (46.48 J K À1 mol À1 ) for this latter quantity. The thermal relaxation kinetics and solvatochromic behaviour of the derivatives in a range of solvents of differing polarity (ethanol, dichloromethane, acetone, toluene and diethyl ether) are also presented. Differences in the estimated values of these thermodynamic and kinetic parameters are discussed with reference to the molecular structure of the derivatives.

Hydrogen‐Bonded Dimeric Capsules with Appended Spiropyran Units: Towards Controlled Cargo Release

“…It also indicated that the SP−C[4]A tetra‐ureas may be degraded (not photo‐stable) under the long irradiation conditions used to achieve the PSS. [46] We obtained similar results using the calix[4]pyrrole counterpart all‐SP−C[4]P (Figure S19).…”

First thermal studies on visible-light-switchable negative T-type photochromes of a nitrile-rich series

“…[12][13][14] In the case of T-type photochromes, this feature is important and exciting because it allows to control the stability of the photoinduced form by changing the temperature conditions. This issue has been well studied for known groups of photochromes, such as spiropyrans, 15,16 spirooxazines, 17 azobenzenes, 18,19 diarylethenes, 20,21 dihydropyrene, 22 dihydroindolizines 23 and bindone derivatives. 24 Papers [15][16][17][18][19][20][21][22][23][24] also demonstrate that the analysis of the temperature effect on the rate constant allows to estimate various important energy parameters of the reverse thermal reaction of photochromes, for example activation energy.…”

Thiophene-Based Trimers and Their Bioapplications: An Overview

“…Various trimer carboxylic acids have been prepared, directly connected to the thiophene rings [ 342 , 343 , 344 , 345 ] or linked through a spacer. In fact, spacers of one [ 346 , 347 , 348 , 349 , 350 , 351 , 352 ], two [ 279 , 353 , 354 ], three [ 355 ], four [ 354 ], five [ 356 ] or six [ 350 ] carbon atoms are reported ( Scheme 18 , I and II).…”

“…The negative charge of carboxylic acid is widely exploited for promoting attractive interactions between the trimer and other molecules, materials or surfaces [ 349 , 350 , 355 , 358 , 359 ]. Additionally, trimers carrying a carboxylic acid can be easily functionalized by esterification or amidation [ 343 , 346 , 347 , 360 ].…”

“…The alcohol [ 250 , 253 , 273 , 274 , 275 , 277 , 364 , 365 , 368 , 369 ] or the carboxylic acid [ 302 , 343 , 344 , 346 , 347 ] on the trimer is exploited for this purpose ( Scheme 19 , I and II). In this way, several molecules, nanoparticles and other functional materials were covalently linked to the trimers, including spyropyran [ 343 , 370 ], gold nanoparticles [ 371 ], poly(ethylene glycol) [ 302 , 372 ], cellulose [ 373 ], methaclyate [ 277 ], thiocarbonylthio derivate useful for RAFT (Reversible addition−fragmentation chain-transfer) polymerization [ 275 ] and olefin dendrons [ 374 ]. Numerous works report the preparation of the 3′,4′ trimer diester ( Scheme 19 , III) [ 242 , 361 , 362 , 366 , 375 , 376 ].…”