Lanthanide and actinide complexes of diphosphazane dioxides and lanthanide complexes of amino acids and peptides

Abstract

The chemistry of f-block elements is currently undergoing rapid developments, and a rich and diverse chemistry is emerging because of its various applications (e.g., MOCVD precursors, MRI contrast agents). In addition, lanthanide ions are widely used as probes for biological processes. The present research programme is concerned with synthetic, spectroscopic, and structural studies on lanthanide and actinide complexes of some new diphosphazane dioxides, as well as lanthanide complexes of amino acids and peptides.

Diphosphazane Dioxides and Lanthanide Complexes Synthetic strategies have been developed for diphosphazane dioxides of the type: {X2P(O)}2NR\{ X_2P(O) \}_2NR{X2?P(O)}2?NR These compounds have been characterised by various spectroscopic methods, and a few of these, viz., {X2P(O)}2NR{X=OPh,R=Me;X=Ph,R=Pri}\{ X_2P(O) \}_2NR \quad \{ X = OPh, R = Me; X = Ph, R = Pri \}{X2?P(O)}2?NR{X=OPh,R=Me;X=Ph,R=Pri} and Ph2P(O)NPr?P(O)Ph(OC6H4N?2)Ph_2P(O)NPr'P(O)Ph(OC_6H_4N-2)Ph2?P(O)NPr?P(O)Ph(OC6?H4?N?2) have been structurally characterised. Lanthanide nitrate complexes of symmetrical diphosphazane dioxides, having the composition: [Ln(NO3)3(L?L)2](L?L={Ph2P(O)}2NPr? or {(PhO)2P(O)}2NMe)[Ln(NO_3)_3(L-L)_2] \quad (L-L = \{ Ph_2P(O) \}_2NPr' \text{ or } \{ (PhO)_2P(O) \}_2NMe)[Ln(NO3?)3?(L?L)2?](L?L={Ph2?P(O)}2?NPr? or {(PhO)2?P(O)}2?NMe) have been prepared and characterised. The structure of one of the complexes, viz., [Pr(NO3)3({(PhO)2P(O)}2NMe)2][Pr(NO_3)_3(\{ (PhO)_2P(O) \}_2NMe)_2][Pr(NO3?)3?({(PhO)2?P(O)}2?NMe)2?] is established by X-ray crystallography.

Uranyl and Thorium Complexes Uranyl nitrate complexes of the diphosphazane dioxides {(PhO)2P(O)}2NMe,{Ph2P(O)}2NPr?,{Ph2P(O)}2N(5??CHMePh),Ph2P(O)N(Pri)P(O){Ph(OC6H4Me??)},Ph2P(O)NPr?P(O)?(O2C12H8)\{ (PhO)_2P(O) \}_2NMe, \{ Ph_2P(O) \}_2NPr', \{ Ph_2P(O) \}_2N(5-\ast CHMePh), Ph_2P(O)N(Pri)P(O)\{Ph(OC_6H_4Me-\ast)\}, Ph_2P(O)NPr'P(O)-(O_2C_{12}H_8){(PhO)2?P(O)}2?NMe,{Ph2?P(O)}2?NPr?,{Ph2?P(O)}2?N(5??CHMePh),Ph2?P(O)N(Pri)P(O){Ph(OC6?H4?Me??)},Ph2?P(O)NPr?P(O)?(O2?C12?H8?) have also been prepared. A single-crystal X-ray diffraction study confirms the structures of [UO2(NO3)2(L?L)](L?L={Ph2P(O)}2NPr? or {(PhO)2P(O)}2NMe)[UO_2(NO_3)_2(L-L)] \quad (L-L = \{ Ph_2P(O) \}_2NPr' \text{ or } \{ (PhO)_2P(O) \}_2NMe)[UO2?(NO3?)2?(L?L)](L?L={Ph2?P(O)}2?NPr? or {(PhO)2?P(O)}2?NMe) An unusual dimeric uranyl complex bridged by a peroxo group, [{UO2(NO3)({(PhO)2P(O)}2NMe)}2(???2??2?O2)][\{ UO_2(NO_3)(\{ (PhO)_2P(O) \}_2NMe) \}_2(\mu-\eta^2-\eta^2-O_2)][{UO2?(NO3?)({(PhO)2?P(O)}2?NMe)}2?(???2??2?O2?)] has been isolated and structurally characterised. Treatment of Th(NO?)? with the diphosphazane dioxide {Ph2P(O)}2NPr?\{ Ph_2P(O) \}_2NPr'{Ph2?P(O)}2?NPr? yields a different type of complex, viz., [Th({Ph2P(O)}2NPr?)3(NO3)2]2+[Th(NO3)6]2?[Th(\{ Ph_2P(O) \}_2NPr')_3(NO_3)_2]^{2+}[Th(NO_3)_6]^{2-}[Th({Ph2?P(O)}2?NPr?)3?(NO3?)2?]2+[Th(NO3?)6?]2? containing ten-coordinated cationic and twelve-coordinated anionic moieties, as revealed by X-ray crystallography.

Lanthanide Complexes with Amino Acids and Peptides To probe the binding of lanthanide ions to proteins, it is necessary to understand the mode of binding of lanthanides with various amino acids and peptides. In this context, lanthanide complexes of:

?-aminoisobutyric acid (Aib) 1-amino-cyclohexyl-1-carboxylic acid (Acc6) glycylglycylglycine (GGG)

have been prepared and characterised by analytical and spectroscopic methods. Single-crystal X-ray diffraction studies have been carried out on:

Aib complexes of Ln(ClO?)? (Ln = La, Dy) and PrCl? Acc6 complexes of Ln(ClO?)? (Ln = Nd, Er) GGG complexes of Ln(ClO?)? (Ln = Eu, Dy)

For the first time, a unidentate coordination of an amino acid to lanthanides is observed in the Nd perchlorate complex of Acc6.