Sandwich-Type Tetranuclear Lanthanide Complexes with Cucurbit[6]uril: From Molecular Compounds to Coordination Polymers

Abstract

Sandwich-type lanthanide complexes with macrocyclic ligand cucurbit[6]uril (C 36H 36N 24O 12, CB[6]) were synthesized under hydrothermal conditions from aqueous solutions of lanthanide(III) bromides, CB[6], and 4-cyanopyridine. According to X-ray analysis (Ln = La, Pr, Dy, Ho, Er, and Yb), the compounds with different structural types of lanthanide cores have a common fragment where the tetranuclear hydroxo complex is sandwiched between two macrocycles {(IN@CB[6])Ln 4(mu 3-OH) 4(IN@CB[6])} (6+) (IN = isonicotinate). The photoluminescence (for Ln = Eu) and Fourier transform ion cyclotron resonance mass spectra (for Ln = Pr, Dy, and Er) were studied. The compounds are used for the first time as precursors for the synthesis of lanthanide-silver heterometallic coordination polymers. The chainlike crystal structure of polymers (Ln = La, Pr, and Dy) is constituted by the sandwich complexes linked via the coordination of IN nitrogen atoms to the silver atoms.

Simple Coordination Complexes of Cucurbit[n]urils with Metal Ions

“…2.14b). Generally, Q [6] molecules show affinity to alkali and alkaline earth metal ions, and form molecular bowls or capsules [37][38][39]. However, their interaction with metal ions in the presence of a third species could result in the formation of novel coordination polymers and supramolecular assemblies, which will be described in detail later.…”

“…There are a few exceptions to the usual products, such as Q [6]/Ag + complexes from a solution containing a Q [6]/isonicotinic acid/La 3+ host-guest complex in the presence of AgNO 3 , as shown in Fig. 2.14c [39]. Another is the complex formed by tetramethyl-substituted Q [6] (TMeQ [6]) and AgNO 3 [40,41].…”

“…Fedin and coworkers have synthesized a series of polynuclear lanthanide complexes by reacting Q [6] with aqueous solutions of lanthanide(III) nitrates [51], chlorides [52] or bromides [39], Q [6], and 4-cyanopyridine under hydrothermal conditions (130 °C). These μ-hydroxo polynuclear lanthanide complexes are formed in aqueous solution and their formation involves hydrolysis of the corresponding Ln 3+ salts with, under the conditions employed, the 4-cyanopyridine also being hydrolyzed to isonicotinic acid.…”

One-Dimensional Coordination Polymers of Lanthanide Cations to Cucurbit[7]uril Built Using a Range of Tetrachloride Transition-Metal Dianion Structure Inducers

“…Cucurbit[n]urils(Q[n]s) [9][10][11][12][13][14] consist of a rigid hydrophobic cavity of low polarity, accessible through two open polar portals rimmed with carbonyl groups, which can interact with various metal ions [15][16][17][18][19][20][21][22][23][24][25][26], or their complexes [27][28][29][30][31][32][33][34][35][36][37][38][39][40] or clusters [41][42][43][44][45][46][47][48][49][50] [53]. In recent years, there has been a trend towards introducing an organic or inorganic species into the metal-Q[n] systems as a "structure inducer" or trigger, since the properties, structural novelties, and functionalities of the resulting coordination polymers have often exceeded those observed in the absence of such agents.…”

“…In recent years, there has been a trend towards introducing an organic or inorganic species into the metal-Q[n] systems as a "structure inducer" or trigger, since the properties, structural novelties, and functionalities of the resulting coordination polymers have often exceeded those observed in the absence of such agents. Following on from Fedin's work [30,32], Thuéry focused on the Q[n] complexation of lanthanides and actinides and demonstrated the formation of a series of lanthanide-Q[n] and uranyl-Q[n] supramolecular assemblies in the presence of added organic ligands [34][35][36][37]. Since a novel potassium-Q [5] supramolecular network was first prepared in the presence of p-hydroxybenzoic acid [60], coordination of metal ions to Q[n]s in the presence of various organic molecules has been extensively studied in our laboratory, and a strategy for inorganic or organic molecule-induced coordination polymers of metal ions to Q[n]s has gradually been established.…”