Solvatochromism and solvation of ternary iron-diimine-cyanide complexes

Solvation of iron(II) complexes of hexadentate tris-diimine Schiff base tripod ligands in alcohol?water and DMSO?water mixtures

“…Such patterns, which suggest maximum solvation of solutes in mixed solvents whose components solvate different parts of the surface of the solute, have been reported previously. Examples of such synergic solvation include ternary complexes [Fe(diimine) 2 (CN) 2 ], where water interacts strongly with the cyanide ligands but organic cosolvents preferentially solvate the hydrophobic diimine periphery [24,28], tris(8-hydroxyquinolinato)aluminium(III) and its iron (III) analogue [29], and tris(3-hydroxy-4-pyranonate) and tris(3-hydroxy-4-pyridinonate) complexes of such metal(III) centres as Fe 3þ , Al 3þ , and In 3þ [30]. Indeed the 2-ethyl-3-hydroxy-4-pyranone and 1,2-dimethyl-3-hydroxy-4-pyridinone ligands (ethylmaltol and L1 or deferiprone) themselves show synergic solvation [31].…”

“…These comparisons are with the aqua-ion Fe 2þ aq [23], with the hydrophilic nitroprusside anion [Fe(CN) 5 (NO)] 2À [2] and the predominantly hydrophilic complex [Fe(CN) 4 (bipy)] 2À [24], with the marginally lipophilic complex [Fe(hxsb)] 2þ of the hexadentate Schiff base (3) with R = H [25], and with the increasingly lipophilic complexes [Fe(phen) 3 ] 2þ [26] and [Fe(Me 2 bsb) 3 ] 2þ ðMe 2 bsb ¼ ð4ÞÞ [27]. Figure 1 shows that the [Fe(fpyPhg 3 tren)] 2þ cation presents a surface to the surrounding solvent of high lipophilicity, comparable with that of the [Fe(Me 2 bsb) 3 ] 2þ cation, hitherto the most lipophilic of iron(II)-diimine complexes.…”

Solvatochromism and solvation of transition metal complexes in ternary aqueous solvent media

“…92-93 of reference [6]). In binary solvent mixtures, charge-transfer wavelengths (frequencies) are useful indicators of preferential solvation, as has been demonstrated, for e.g., several [Fe(CN) 2 (diimine) 2 ] compounds in binary organic solvent mixtures [15,[23][24][25][26] and for [Fe(CN) 2 (bipy) 2 ] in alcohol-water mixtures [26,27]. Solvatochromic inorganic complexes of this type have also been used to monitor solvation in salt solutions [28] and to probe their environment in organised aqueous media such as micelles and microemulsions [28,29].…”

Donor and acceptor number effects for the solvatochromic behaviour ofbis-(2,2?-bipyridyl)-bis-cyanoiron(II) in binary aqueous mixtures

“…This can be defined as the solvent dependence of the frequency of an electronic transition. Solvatochromism of ternary low spin iron(II) complexes of the Fe(CN)2(diimine)2 type have been recently described by a variety of authors [9][10][11]. In a recent paper [12], solvent effects and correlation with Reichardt's E T values on charge transfer spectra of the title complex have been made.…”