β-Cyclodextrin-Assisted Intervalence Charge Transfer in Mixed-Valent [2]Rotaxane Complexes Having Metal Centers Linked by an Interrupted π-Electron System

Abstract

FeII to RuIII electron transfer is initiated by the inclusion of saturated bridging ligands into the β‐cyclodextrin (CD) cavity of [2]rotaxane complexes and is observed as an intervalence charge transfer (IVCT) band in the electronic spectra (see picture). The rotaxanes are synthesized by using RuIII and FeII complexes as stoppers, β‐CD as the cyclic molecular head, and 4,4′‐bipyridine derivatives with interrupted π‐electron system as the bridging ligand between the metal centers.

Intervalence charge transfer transition in mixed valence complexes synthesised from RuIII(edta)- and FeII(CN)5-cores

“…) is observed; though value for this is found to be lower (table 1) than that observed for [{(edta)Ru(bpp)Fe(CN) 5 }] 4and related complexes [8][9][10][11][12][13][14][15]16 . The net decrease in the rate constant for forward reaction (k f ) is presumably due to enhanced steric and electronic hindrance that result from the β-CD inclusion of the heterocyclic spacer group.…”

“…Procedures for synthesis of various ligands, mono-and bi-nuclear complexes (I-VIII) are described in earlier reports [8][9][10][11][12][13] . Here we have described briefly the synthetic methodology for semirotaxane (IX, X) and [2]rotaxane complexes (XI, XII).…”

Cyclodextrin‐Based Rotaxanes: from Rotaxanes to Polyrotaxanes and Further to Functional Materials

“…The rotaxanes were purified by ion‐exchange chromatography and recovered in reasonable yields. The same type of CD‐based rotaxanes capped with coordination bonding was also synthesized using cobalt, iron, and ruthenium complexes . Hannak and co‐workers synthesized a CD‐based rotaxane by coupling of 1,12‐dibromododecane with vitamin B12 in the presence of α‐CD through the formation of stable Co–C bond.…”

Self assembled rotaxane and pseudo-rotaxanes based on beta-cyclodextrin inclusion compounds with trans-1,4-bis[(4-pyridyl)ethenyl]benzene-pentacyanoferrate(II) complexes

“…2 Their ability to include guest molecules arises from the hydrophobic internal environment, suitable for accommodating aromatic molecules, [3][4][5] water insoluble drugs, [6][7][8] and inorganic compounds. [9][10][11][12][13][14][15] Such inclusion compounds result from the energetically unfavorable interaction between the included water molecules in the hydrophobic CD cavity on one hand, and between water and guest on the other, in comparison with the hydrophobic and/or van der Waals interactions between the guest and the host cavity.…”