The role of a weakly coordinating thioether group in ligation controlled molecular self-assemblies and their inter-conversions in Ni(ii) complexes of l-methionine derived ligand

A series of Ni(ii) complexes of an amino acid derived ligand (Salmet) has been synthesized, and characterized by various techniques including X-ray crystallography. Alkali ions K⁺/Na⁺ direct the conversion of monomers to multi-nuclear complexes.

Solvent effect on neutral chiral supramolecular assemblies and their distinct receptor behaviour towards anions

We describe the distinct receptor behaviour of a neutral chiral Cu(ii) complex in dimethylsulfoxide or methanol towards anions, such as F(-), Cl(-), Br(-), I(-) or OAc(-), where F(-) and OAc(-) show the most colorimetric change, through various spectroscopic techniques. Further insights into this at the molecular level come from the single crystal X-ray structures of both dimethylsulfoxide and methanol solvates which show a solvent effect on their supramolecular network formation. Both chromogenic and fluorogenic sensing of the anions indicate a 2 : 1 receptor-anion formation via anion-π as well as hydrogen bonding interactions.

Controlling the self-assembly of homochiral coordination architectures of CuII by substitution in amino acid based ligands: synthesis, crystal structures and physicochemical properties

In this paper we report six chiral ligands based on l-tyrosine, l-serine and l-phenylalanine and their homochiral Cu^II complexes to study the effect of various substitutions in the ligands on the formation of diverse coordination architectures.

Photocytotoxicity of copper(II) complexes of curcumin and N-ferrocenylmethyl-L-amino acids

Copper(II) complexes [Cu(Fc-aa)(cur)] (1-3) of curcumin (Hcur) and N-ferrocenylmethyl-L-amino acids (Fc-aa), viz., ferrocenylmethyl-L-tyrosine (Fc-TyrH), ferrocenylmethyl-L-tryptophan (Fc-TrpH) and ferrocenylmethyl-L-methionine (Fc-MetH), were prepared and characterized. The DNA photocleavage activity, photocytotoxicity and cellular localization in HeLa and MCF-7 cancer cells of these complexes were studied. Acetylacetonate (acac) complexes [Cu(Fc-aa)(acac)] (4-6) were prepared and used as controls. The chemical nuclease inactive complexes showed efficient pUC19 DNA cleavage activity in visible light. Complexes 1-3 showed high photocytotoxicity with low dark toxicity thus giving remarkable photodynamic effect. FACScan analysis showed apoptosis of the cancer cells. Fluorescence microscopic studies revealed primarily cytosolic localization of the complexes.

Sodium and potassium ion directed self-assembled multinuclear assembly of divalent nickel or copper and L-leucine derived ligand

L-leucine derived ligand (H(2)L(L-leu)), KOH, and Ni(II) salt in 2:2:1 ratio self-assembled into a rather large (approximately 13 A) supramolecular assembly with the formula [K{Ni(HL(L-leu))(2)}(3)](+) (1). Structural characterization showed three [Ni(HL(L-leu))(2)] units encapsulated K(+) similar to organic crown ethers/cryptand. Substituting Ni(II) with Cu(II) and K(+) with Na(+) in the above reaction resulted in a set of structurally identical assemblies with the general formula [M'{M(HL(L-leu))(2)}(3)](+), where M' is either K(+) or Na(+) and M is either Cu(II) or Ni(II); [Na{Ni(HL(L-leu))(2)}(3)]ClO(4) (2), Na{Ni(HL(L-leu))(2)}(3)]OTf (3), [K{Cu(HL(L-leu))(2)}(3)]ClO(4) (4), [Na{Cu(HL(L-leu))(2)}(3)]ClO(4) (5), [K{Cu(HL(L-leu))(2)}(3)]NO(3) (6). Electrospray Ionization (ESI)-mass spectra of the assemblies in MeOH showed the retention of assemblies in solution. Visible spectroscopic studies showed retention of assembly 1 in N,N-dimethylformamide (DMF) which is stable even after the addition of 5 equiv of [18]-crown-6. The assemblies in 2-6 show various degrees of dissociation to [M(HL(L-leu))(2)] and M', in stronger H-bonding methanol. The dissociation can be reversed upon addition of excess KNO(3)/NaNO(3) salt. Structural characterization of [Cu(HL(L-leu))(2)(MeCN)] (7) along with its transformation to [K{Cu(HL(L-leu))(2)}(3)](+) in the presence of K(+) salt demonstrated that the assembly formation proceeds through an alkali metal ion induced ligand reorientation within the [Cu(HL(L-leu))(2)] units which is further stabilized by six strong H-bonds holding the assembly. Interestingly, visible spectra of 1 and 2 shows that minor structural changes caused by replacing K(+) with Na(+) is sufficient to shift the d-d transition of Ni(II) by approximately 70 nm, thereby providing an indirect way of distinguishing K(+) and Na(+), none of which have spectroscopic signature in the visible range.