The surprising lability of bis(2,2’:6’,2’’-terpyridine)- chromium(III) complexes

The complex [Cr(tpy)(O3SCF3)3] (tpy = 2,2′:6′,2′′-terpyridine) is readily made from [Cr(tpy)Cl3] and is a convenient precursor to [Cr(tpy)2][PF6]3 and to [Cr(tpy)(4′-(4-tolyl)tpy)][PF6]3 and [Cr(tpy)(5,5′′-Me2tpy)][PF6]3 (4′-(4-tolyl)tpy = 4′-(4-tolyl)-2,2′:6′,2′′-terpyridine; 5,5′′-Me2tpy = 5,5′′-dimethyl-2,2′:6′,2′′-terpyridine); these are the first examples of heteroleptic bis(tpy) chromium(III) complexes. The single crystal structures of 2{[Cr(tpy)2][PF6]3}·5MeCN, [Cr(tpy)(4′-(4-tolyl)tpy)][PF6]3·3MeCN and [Cr(tpy)(5,5′′-Me2tpy)][PF6]3·3MeCN have been determined. Each cation contains the expected octahedral {Cr(tpy)2}3+ unit; in all three structures, the need to accommodate three anions per cation and the solvent molecules prevents the formation of a grid-like array of cations that is typical of many lattices containing {M(tpy)2}2+ motifs. Three reversible electrochemical processes are observed for [Cr(tpy)(4′-(4-tolyl)tpy)][PF6]3 and [Cr(tpy)(5,5′′-Me2tpy)][PF6]3, consistent with those documented for [Cr(tpy)2]3+. At pH 6.36, aqueous solutions of [Cr(tpy)2][PF6]3 are stable for at least two months. However, contrary to the expectations of the d3 Cr3+ ion being a kinetically inert metal centre, the tpy ligands in [Cr(tpy)2]3+are labile in the presence of base; absorption and 1H NMR spectroscopies have been used to monitor the effects of adding NaOH to aqueous and CD3OD solutions, respectively, of the homo- and heteroleptic complexes. Ligand dissociation is also observed when [Bu4N]F is added to CD3OD solutions of the complexes, but in aqueous solution, [Cr(tpy)2][PF6]3 is stable in the presence of fluoride ion

Homoleptic and heteroleptic complexes of chromium(III) containing 4'-diphenylamino-2,2':6',2''-terpyridine ligands

Two heteroleptic bis(2,2′:6′,2″-terpyridine)chromium(III) complexes [Cr(1)(4′-(4-tolyl)tpy)][CF3SO3]3 and [Cr(2)(4′-(4-tolyl)tpy)][CF3SO3]3 (1 = 4-([2,2′:6′,2″-terpyridin]-4′-yl)-N,N-diphenylaniline, 2 = 4-([2,2′:6′,2″-terpyridin]-4′-yl)-N,N-bis(4-methoxyphenyl)aniline, 4′-(4-tolyl)tpy = 4′-(4-tolyl)-2,2′:6′,2″-terpyridine) have been prepared and their spectroscopic and electrochemical properties compared with those of [Cr(4′-(4-tolyl)tpy)2][CF3SO3]3 and [Cr(1)2][CF3SO3]3. The single crystal structure of [Cr(4′-(4-tolyl)tpy)2][CF3SO3]3·2MeCN is presented, and the effects of accommodating three triflate anions and two MeCN molecules per cation are discussed in terms of related structures. The coordination of 1 or 2 to chromium(III) red-shifts the intra-ligand charge transfer (ILCT) band and this band exhibits a negative solvatochromic effect in some solvents. However, in H2O, MeOH, DMSO and DMF, the tpy ligands are labile; changes in the absorption spectra of solutions of [Cr(2)(4′-(4-tolyl)tpy)][CF3SO3]3 are consistent with the formation of [Cr(4′-Xtpy)(Solv)3]3+ (Solv = solvent) rather than complete ligand displacement or a ligand redistribution

Heteroleptic chromium(III) tris(diimine) [Cr(N^N)2(N'^N')]3+ complexes

A series of heteroleptic tris(diimine) complexes of chromium(III) is reported and the crystal structures of {4[Cr(bpy)2(phen)][PF6]3}·11MeCN and 4[Cr(4,4′-Me2bpy)2(bpy)][PF6]3}·12MeCN·H2O are described. The combined effects of a 1:3 cation: anion ratio and lattice solvent molecules are discussed, in particular in the context of the influence on intercation embraces. The presence of the methyl substituents in {4[Cr(4,4′-Me2bpy)2(bpy)][PF6]3}·12MeCN·H2O results in Me–πbpy contacts becoming the dominant packing interactions and in the assembly of motifs distinct from those in {4[Cr(bpy)2(phen)][PF6]3}·11MeCN

Urban semiosis: Creative industries and the clash of systems

© The Author(s) 2014. This article has two aims. The first is to make the case that the ‘universe of the mind’ imagined by Yuri Lotman may be considered as a foundational model for cultural evolution (population-wide, dynamic, autopoietic, self-organising adaptation to changing environments). The second aim is to take forward a model of culture derived from Lotman’s work – a model I call ‘the clash of systems’ – in order to apply it to creative industries research. Such a move has the salutary effect of putting the ‘universe of the mind’ literally in its place. That place, now, predominantly, is in the city. Thus, the article uses Lotman’s model of the semiosphere to link different complex systems, principally the semiosphere with that of the city, in order to explore the productive potential of encounters – clashes – between different systems. Applying these insights to the field of creative industries research, the article proposes that creative culture in the globalised, urban and web-connected era can be characterised as ‘urban semiosis’

Heteroleptic chromium(III) tris(diimine) [Cr(N^N)2(N'^N')]3+ complexes

A series of heteroleptic tris(diimine) complexes of chromium(III) is reported and the crystal structures of {4[Cr(bpy)2(phen)][PF6]3}·11MeCN and 4[Cr(4,4′-Me2bpy)2(bpy)][PF6]3}·12MeCN·H2O are described. The combined effects of a 1:3 cation: anion ratio and lattice solvent molecules are discussed, in particular in the context of the influence on intercation embraces. The presence of the methyl substituents in {4[Cr(4,4′-Me2bpy)2(bpy)][PF6]3}·12MeCN·H2O results in Me–πbpy contacts becoming the dominant packing interactions and in the assembly of motifs distinct from those in {4[Cr(bpy)2(phen)][PF6]3}·11MeCN

Single emitter switching based multicolor nanoscopy

By switching conventional dyes into long-lived dark states we can record their fluorescence time-sequentially even if they are closely packed. This allows for simultaneous nanoscale imaging of up to four dye species with minimal cross-talk. © 2010 Optical society of America

Single emitter switching based multicolor nanoscopy

By switching conventional dyes into long-lived dark states we can record their fluorescence time-sequentially even if they are closely packed. This allows for simultaneous nanoscale imaging of up to four dye species with minimal cross-talk. © 2010 Optical society of America