Halide-Templated Assembly of Polynuclear Lanthanide-Hydroxo Complexes

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.

Synthesis and Spectroscopic Characterization of <i>l</i>-Aspartic Acid Complexes with Metals of the Lanthanides Family

“…A peak around 3505 cm -1 , previously reported and assigned to the stretching of a  3 -OH [13], was not observed in any of all the compounds; the peak is probably obscured by the broad water absorption. …”

“…The compounds were characterized using a variety of techniques, including IR, 13 C NMR, 1 H NMR, microanalysis (CHN) and metal content. The metal content was determined by complexometric titration with EDTA.…”

“…Yield = 0.20 g (48,42 %). The presence of lanthanum metal was detected by xylenol orange indicator, 13 …”

Anion‐Templated Synthesis

“…Halides have proven to effectively direct the synthesis of several metallamacrocycles. Hawthorne et al reported the first example of such halide-templated species in 1991 with the tetranuclear [12]mercuracarborand-4 (1; Scheme 1). [10] Compound 1 was prepared by reacting 1,2-dilithiocarborane with mercury(ii) in the presence of chloride ions.…”

“…[12] These polynuclear hydroxolanthanide compounds were synthesized by the tyrosinecontrolled hydrolysis of lanthanide perchlorates in the presence of specific halides. The pentadecanuclear complexes with a core formula [Ln 15 (m 3 -OH) 20 (m 5 -X)] 24+ (X = Cl, Br; Ln = Eu, Nd, Gd, Pr, Eu) were formed when the added halide was either chloride or bromide (Figure 1).…”