Supramolecular solvatochromism. Effect of solvents on the self-assembly and charge transfer absorption characteristics of lipid-packaged, linear mixed-valence platinum complexes

Abstract

Lipid-packaged, mixed-valence linear platinum complexes are dispersed in chloroform, chlorocyclohexane and in methylcyclohexane. They show indigo-colors, which are identical to solid samples. These lipid-complexes display supramolecular thermochromism, resulting from heat-induced dissociation and recovery of coordination chains. Unexpectedly, reassembled samples show altered CT absorption spectra. In chloroform, the reassembled complex gives indigo-color, while the chlorocyclohexane and methylcyclohexane dispersions show blue and red-colors, respectively. These color changes indicate enhanced solvation of lipid-packaged platinum complexes after the heat treatment. The thermal re-assembly also affects the aggregate morphology, and leads to the formation of nanowires, nanofibers and nanoparticles depending on the solvents employed. The conversion of pseudo one-dimensional (1D) inorganic complexes to lipophilic supramolecular assemblies thus gives solvatochromic properties, which are elements not existing in the conventional solid-state inorganic chemistry.

Helical-Ribbon and Tape Formation of Lipid Packaged [Ru(bpy)3]2+ Complexes in Organic Media

“…Ruthenium complex with lipid amphiphiles 1 – 6 were synthesized based on the literature procedures [20,61,62,63,64,65,66,67,68] (Figure 1, see subchapter 3–1). The metal complexes were obtained by replacement of counter anion of [Ru II (bpy) 3 ] 2+ to lipid amphiphiles [20].…”

“…In this context, amphiphilic supramolecular strategies using lipids have been developed to construct nano-assembly of coordination compounds [49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65]. Especially, self-assembled nanowires by amphiphilically modified coordination compounds have been developed [54,55,56,57,58,59,60,61,62,63,64,65]. Furthermore, lipids with charily and purely enantioselective amino acid play a significant role in the formation of helices of supramolecular composites [20,57,58,59,60,61,62,63,64,65].…”

“…Especially, self-assembled nanowires by amphiphilically modified coordination compounds have been developed [54,55,56,57,58,59,60,61,62,63,64,65]. Furthermore, lipids with charily and purely enantioselective amino acid play a significant role in the formation of helices of supramolecular composites [20,57,58,59,60,61,62,63,64,65]. The introduction of lipid counter anions to cationic metal complexes can lead to the dispersion of nanowires, nanosheet, and tubes in organic media, resulting in the emergence of functionality not available in the solid state [20,54,55,56,57,58,59,60,61,62,63,64,65].…”

Solvent Effects in Supramolecular Systems

“…The electronic spectra of the as described supramolecular complex were found to be readily influenced by solvent polarity and that the packaging of the complex is vital for the overall medium-responsive properties. Some years later, Kuroiwa et al reported on the supramolecular solvatochromism of lipid-packaged, mixed-valence linear platinum complexes (Figure 14) which were investigated in dispersions employing the solvents CHCl 3 , chlorocyclohexane, and methylcyclohexane [54]. It was found that solid samples were all indigo-colored but displayed supramolecular thermochromism, attributed to heat-induced dissociation and concomitant recovery of coordination chains.…”

Self-assembly and functionalization of lipophilic metal-triazole complexes in various media

“…We have developed a creative approach to disperse halogen-bridged, mixed-valence platinum complexes in organic media as lipidpackaged nanowires. [9][10][11][12][13][14][15][16][17][18][19] These nanowires exhibit supramolecular thermochromism, 12-14 solvatochromism 16,17,19 and nano assembly into pillared honeycomb stereo architectures. 18 On the other hand, 1,2,4-triazoles are known to act as bridging ligands and their linear metal complexes have been actively investigated because of their polymeric structures and magnetic interactions between linearly aligned metal ions.…”