Unsymmetrical chiral salen Schiff base ligands

Bidentate ligands templated by a convex trimetallic bis(salphen) platform

“…A disadvantage is that usually a mixture of symmetric and nonsymmetric products is formed. Different strategies have been developed to circumvent this problem, such as monoprotonation of the diamine [28][29][30] or the stepwise addition of the two different aldehydes to the diamine [31]. Another efficient and elegant strategy is based on the low reactivity of ketones compared to aldehydes in the condensation reaction [32].…”

Nonsymmetrically Substituted Uranyl-Salophen Receptors: New Opportunities for Molecular Recognition and Catalysis

“…It is easy to understand that the synthetic approach toward non symmetrical metal-salophen complexes cannot be so straightforward. In the literature there is a certain number of examples dealing with the synthesis of nonsymmetrical salen complexes, 18,19,20,21,22 while fewer are those concerning also salophen derivatives. 23,24 Insert 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 F o r P e e r R e v i e w O n l y 4 There is more than one possibility to break the symmetry of the complex.…”

“…This is then added to one equivalent of a second salicylaldehyde derivative in the presence of triethylamine to produce the desired product. Also Gilheany et al 22 tried to follow this strategy of trapping the mono-Schiff base, but the poor results obtained prompted them to continue with chromatographic separation of reaction mixtures in which all the three possible combination of the reagents are present. As far as we know, no similar procedure has been adopted to synthesize nonsymmetrical metal salophen complexes.…”

Synthesis, characterization and catalytic activity of neat and alumina supported trans-(diaqua)(N,N-ethylene-bis-salicylamide)chromium(III): a comparative study

“…Transition metal complexes having quadridentate Schiff base ligands like Salen {N,N 0 -bis(salicylidene)ethane-1,2-diamine} and its prototype have continued to be an active area of research because of their potential applications in catalytic [1][2][3][4][5][6][7][8][9][10] and biological [11][12][13] processes. Schiff bases with different substituents in the ligand peripheries lead to substantially different solid-state structures and reactivities.…”