Search

The photoreversible transportation of Zn2+ions across an interface using photochromic substitutedspirobenzopyrans has been demonstrated. The inclusion of strategically placed sterically influencing 3′methyl3band 3spirocyclohexyl3cgroupings 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 ringopening↔closing reactions of two skeletally identical spirobenzopyrans 4and 5, but possessing “electronicallymodifying” 5trifluoromethylsubstitutents have been studied by 1H NMR spectroscopy: this has enabled us to realise the additional biasing, on the ringopening↔closing process, excerpted on these systems through both selectively placed, inductively controlling functionalgroup substitution andor, simultaneously, sterically influencing group substitution. © WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008

The reversible photochemical ion chelation of the newly synthesised substituted N,N′-bis(spiro[1-benzopyran-2,2′-indolyl])diazacrown systems 15a–c and the subsequent molecular electronic control of this process using appropriately placed substituent groups on the spiro-benzopyran skeleton is reported. The principle of molecular electronic control of ion chelation is demonstrated by comparing the behaviour of the newly synthesised nitro-substituted and pyrido-annulated spiro-benzopyran system 9b with that of the unsubstituted compound 9a. Electronic substituent control over ion chelation is then exemplified for the new N,N′-bis(5′-nitrospiro[1-benzopyran-2,2′-indolyl])diazacrown system 15c and further exemplified for the corresponding 5′-trifluoromethyl derivative 15b, which contains the photochemically more robust trifluoromethyl group. The crown system 15a, unsubstituted in the spiro-indole moiety, is also reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Steric buttressing has been used to effect ene reactions involving conjugated enoic esters under relatively mild conditions and with improved control of observed stereoselectivities.

Ytterbium and neodymium have been shown to exhibit sensitised emission following excitation of pyrene chromophores. Sensitised emission is demonstrated in self-assembled complexes and in azamacrocycle derivatives bearing pendent pyrene groups. Energy transfer in these systems is dependent on the nature of the link between the ligand and the complex.