16917-30-9Relevant academic research and scientific papers
Unusual thermo(photo)chromic properties of some mononitro- and dinitro- substituted 3′-alkyl indolospirobenzopyrans This paper is dedicated to the memory of Dr Thomas G. Nevell.
Abdullah, Ayse,Nevell, Thomas G.,Sammes, Peter G.,Roxburgh, Craig J.
, p. 57 - 72 (2015/06/02)
Isomeric equilbria of dinitro-substituted indolospirobenzopyrans, possessing 3′-gem-methyl- or 3′-cyclohexyl-substitutents, have been investigated using 1H NMR spectroscopy at six temperatures, ranging from 298 K to 410 K; isomerisation processes in a methanolic solution have been monitored by spectrophotometry. For the mononitro-substituted compounds, equilibrium favoured the colourless spirocyclic isomers. Reversion of the coloured merocyanine isomers, generated by UV irradiation, followed first-order kinetics. For the dinitro-substituted compounds the coloured merocyanine isomers predominated. Following decolourisation by visible light photoirradiation, reversion towards the merocyanine structures were particularly slow, absorbances unusually increasing sigmoidally. UV. spectral observations for the gem-methyl- 1 and 3′-cyclohexyl-substituted systems 2 are qualitatively consistent with the simultaneous involvement of two relatively slow rate determining steps, possessing slowly forming and long-lived intermediates - postulated to be the oxygen protonated pyran-ring of the spirocyclic structure and TCC merocyanine isomer, the latter undergoing relatively slow isomerisation about the central β-alkenic bond to the TTC isomer.
Steric and substituent control on the photoreversibility of some novel N-alkyl-3,3′-disubstituted-6-nitro-indolospirobenzopyrans: Evaluation using UV spectroscopic studies
Roxburgh, Craig J.,Sammes, Peter G.,Abdullah, Ayse
experimental part, p. 146 - 162 (2011/12/04)
A series of novel 6-nitro substituted indolospirobenzopyrans are reported. The effects of substitution on their photoreversibility are investigated by: synthesising derivatives that possess sterically hindering (with regard to the spiropyran-opening ? closing) groups contained within the spirocyclic skeleton. Specifically, spirobenzopyrans possessing combinations of various N-alkyl, and/or, simultaneously, 3,3′-geminal methyl and/or cyclohexyl groups are synthesised. Further, these systems are evaluated in three solvents; methanol, acetonitrile and dichloroethane. The thermal decolourisation rates of the gem-dimethyl and 3,3′-cyclohexyl compounds are additionally evaluated at the temperature of 50 °C. The above systems, and changes in physical parameters are extensively evaluated, and the subsequent biasing of the equilibria established using UV spectroscopy. Rates of colourisation, decolourisation and the equilibrium constants are obtained. The overall photochromic 'tuneability' of these systems is subsequently established.
Photoreversible Zn2+ ion transportation across an interface using ion-chelating substituted photochromic 3,3′-indolospirobenzopyrans: Steric and electronic controlling effects
Roxburgh, Craig J.,Sammes, Peter G.,Abdullah, Ayse
experimental part, p. 4951 - 4960 (2009/04/13)
The photoreversible transportation of Zn2+ ions across an interface using photochromic substituted-spirobenzopyrans has been demonstrated. The inclusion of strategically placed sterically influencing 3′-methyl-3b and 3-spirocyclohexyl-3c groupings is investigated and compared to the unsubstituted analogue 3a. Significant control over the spiropyran ringopening? closing reaction, and hence Zn2+ ion transportation has been realised. Additionally, the spiropyran ring-opening? closing reactions of two skeletally identical spirobenzo pyrans 4 and 5, but possessing "electronically-modifying" 5-trifluoromethyl-substitutents have been studied by 1H NMR spectroscopy: this has enabled us to realise the additional biasing, on the ring-opening?closing process, excerpted on these systems through both selectively placed, inductively controlling functional-group substitution and/or, simultaneously, sterically influencing group substitution. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
