Halide-templated assembly of polynuclear lanthanide-hydroxo complexes.

A series of pentadecanuclear lanthanide-hydroxo complexes possessing a common core of the formula [Ln(15)(mu(3)-OH)(20)(mu(5)-X)](24+)(1, Ln = Eu, X = Cl(-); 2, Ln = Nd, X = Cl(-); 3, Ln = Gd, X = Cl(-); 4, Ln = Pr, X = Br(-); 5, Ln = Eu, X = Br(-)) were prepared by L-tyrosine-controlled hydrolysis of corresponding lanthanide perchlorates in the presence of added Cl(-) or Br(-). The cationic cluster core comprises five vertex-sharing cubane-like [Ln(4)(mu(3)-OH)(4)](8+) units centered on the halide template. In the case of templating I(-), dodecanuclear complexes were isolated instead. The core component, [Ln(12)(mu(3)-OH)(16)(I)(2)](18+) (6, Ln = Dy; 7, Ln = Er), consists of four vertex-sharing cubane-like [Ln(4)(mu(3)-OH)(4)](8+) units and exists as a square-shaped cyclic structure with one I(-) located on each side of the square plane. An analogous hydrolytic reaction involving Er(NO(3))(3), L-tyrosine, and NaOH affords the known hexanuclear complex [Er(6)(mu(6)-O)(mu(3)-OH)(8)(NO(3))(6)(H(2)O)(12)](NO(3))(2) whose core component is a face-capped octahedral [Er(6)(mu(6)-O)(mu(3)-OH)(8)](8+) cluster with an interstitial mu(6)-oxo group (Wang, R.; Carducci, M. D.; Zheng, Z. Inorg. Chem. 2000, 39, 1836-1837.). The efficient self-assembly of halide-encapsulating multicubane complexes (1-7) and the inability to produce an analogous nitrate-containing complex demonstrate the superior templating roles played by the halide ion(s). Further credence for the halide template effects was provided by the isolation of the cationic pentadecanuclear complex 3 as the sole product when tyrosine-supported hydrolysis of Gd(NO(3))(3) was carried out in the presence of competitive Cl(-). Magnetic moments of complexes 1-7 measured at room temperature by using Evans' method are in excellent agreement with those calculated by the Van Vleck equation, assuming magnetically noninteractive lanthanide ions.

Coordination Chemistry of Lanthanides at "High" pH: Synthesis and Structure of the Pentadecanuclear Complex of Europium(III) with Tyrosine.

A five-coordinate chloride ion is believed to template the assembly of a pentadecanuclear lanthanide complex of europium(III). This cluster (see picture) has been prepared by coordination of europium(III) perchlorate with tyrosine at about pH 6. Single crystal X-ray analysis established an unprecedented structure in which 15 constituent europium(III) ions are organized into three parallel pentagonal layers.