Investigation of Chromophoric Behavior of Water‐Soluble La III ‐Cu II Polynuclear Metallamacrocyclic 15‐MC‐5 Complex

The visible absorption spectrum of the water soluble polynuclear metallamacrocyclic La III ‐Cu II complex La(H 2 O) 3 [15‐MC Cu(II)Phalaha ‐5](Cl) 3 ( 1 ) based on α‐phenylalaninehydroxamic acid appears to be solvent‐ and ion‐sensitive. The copper(II) d–d transitions of the complex 1 dissolved in methanol, ethanol, water, dimethylformamide, dimethylsulfoxide, pyridine, and N ‐methylpyrrolidone were studied. The chromophoric behavior of complex 1 was investigated in the presence of the Cl – , Br – , I – , HSO 4 – , CO 3 2– , HCO 3 – , H 2 PO 4 – , CN – , SCN – , and N 3 – anions. A considerable change of the d–d transition of the central copper(II) atom was observed for the strongly coordinating cyanide and azide anions. In the presence of HSO 4 – , the d–d intensity of copper(II) also decreased significantly. The molecular structure of La 2 (H 2 O) 7 [15‐MC Cu(II)Phalaha ‐5] 2 (SO 4 ) 4 ( 2 ), obtained as result of the substitution of the coordinated water molecules in 1 by the SO 4 2– anions, was investigated by X‐ray crystallography.