Halide-Templated Assembly of Polynuclear Lanthanide-Hydroxo Complexes

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Abstract
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.

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