William J. Gee

Variation of structural motifs in lanthanoid hydroxo clusters by ligand modification

The isolation of multinuclear lanthanoid clusters with different nuclearities and geometries commenced as a serendipitous discovery and is now the focus of intense research, not only from a coordination chemistry point of view, but also in a variety of applied fields. This perspective analyses the structural library of reported lanthanoid hydroxo clusters to find trends linking their structural motifs with factors such as the specific lanthanoid, the bulkiness of the outer shell of ligands, the coordinating nature of the ligands, and the synthetic methodology. While trends are indeed starting to appear, does this signify that the synthetic chemistry of lanthanoid clusters has now progressed from serendipity to a more rational approach?

Supramolecular architecture of silver(I) coordination polymers containing polydentate N-donor ligands

The reaction of the polydentate N-donor ligands bmtz, H2bmtz, and bptz with various silver salts was investigated. New 1D coordination polymers [Ag2(bmtz) (ClO4)]ClO4 (1), [Ag(bmtz)]ClO4·MeCN (2), [{Ag(tcm)}2(H2bmtz)(MeCN)] (3) and [Ag(bptz)(NO3)] (5), and 2-D sheet structures, [{Ag(tcm)}2bmtz] (4), were synthesized. The structures are built up through the combination of coordination bonds, hydrogen bonding, Ag–π, π–π, and anion–π interactions to generate new supramolecular architectures. The supramolecular structure of the protonated amine salt [H2bptz](NO3)2 (6) is also described.

Single molecule magnetism in a μ-phenolato dinuclear lanthanide motif ligated by heptadentate Schiff base ligands

The heptadentate Schiff base ligand, 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline (H(3)api), yields [Ln(2)api(2)] species when combined with lanthanide salts under basic conditions. A survey of the magnetic properties of this dinuclear lanthanide motif (Ln = Gd, Tb, Dy, Ho) has identified weak magnetic exchange, antiferromagnetic in nature for the isotropic gadolinium analogue, while single molecule magnetic behaviour is displayed in the case of the anisotropic dysprosium complex.

Instantaneous gelation of a new copper(II) metallogel amenable to encapsulation of a luminescent lanthanide cluster

Combining copper(II) chloride, 4-(1H-pyrazol-3-yl)pyridine and triethylamine in dimethylformamide (DMF) results in the instantaneous formation of a metallogel with as little as 0.51 wt% of gelator. The metallogel was found to encapsulate a luminescent lanthanide cluster, yielding a luminescent metallogel.

Systematic study of the formation of the lanthanoid cubane cluster motif mediated by steric modification of diketonate ligands

The treatment of ortho ring-functionalised 1-phenylbutane-1,3-dione ligands bearing nitro (Hnpd, Hnmc), methoxy (Hmmc) or fluoro (Hfpp) groups with hydrated lanthanoid salts has provided [Er(4)(μ(3)-OH)(4)(H(2)O)(2)(npd)(8)] (3), [Ln(4)(μ(3)-OH)(4)(nmc)(8)] (Ln = Gd (4), Tb (5), Dy (6) and Er (7)), [Er(4)(μ(3)-OH)(4)(mmc)(8)] (8) and [Er(4)(μ(3)-OH)(4)(H(2)O)(2)(fpp)(8)] (9), respectively. The products were all obtained as cubane clusters in the solid state, as distinct from previous diketonato clusters, with control over motif formation attributed to the steric influence of the ortho-positioned functional groups at the cluster periphery. This work highlights a means of targeting a specific lanthanoid cluster motif by the rational modification of ligands at key locations.

Caging Peroxide: Anion-Templated Synthesis and Characterization of a Rare-Earth Cluster

Sequestration of peroxide derived from molecular oxygen has resulted in the templated synthesis of a terbium picolinate cluster, isolated as a 2D sodiated network in the solid state. This first example of an air-stable rare-earth peroxide cluster represents key evidence for a peroxide-containing intermediate in rare-earth-cluster-catalyzed oxidation reactions. Luminescent and magnetic properties have also been investigated.

Highly efficient indium(III)-mediated cyclisation of 5-hydroxy-1,3-diketones to 2,3-dihydro-4H-pyran-4-ones; mechanistic insights from in situ Fourier transform infrared spectroscopy

5-Hydroxy-1,3-diketones have been synthesised in a facile one-pot reaction from the treatment of acid chlorides with non-substituted ketones and LiHMDS. Subsequent cyclisation to 2,3-dihydro-4H-pyran-4-ones occurs rapidly and in high yield (89-99%) when mediated by anhydrous indium(iii) chloride. A spectroscopic study of the reaction using in situ Fourier transform infrared (FTIR) spectroscopy has shown the reaction to be highly dependent on temperature, metal complex formation and InCl(3) concentration. Since the reaction is deactivated by the precipitation of [InCl(3).(H(2)O)(3)], the concurrent use of a stronger drying agent, such as molecular sieves 4 A or anhydrous MgSO(4), allows the reaction to be successfully carried out at relatively low loadings of InCl(3) (1-10%). In their absence, the optimum reaction conditions were found to be a diketone : InCl(3) ratio of 3 : 1 in toluene, and a reaction temperature of 80 degrees C.

Coordination polymers of a dipyridylazacrown ligand: structural, thermal and spectroscopic properties

Treatment of the dipyridylazacrown ether ligand N,N′-bis(4-pyridyl-methyl)diaza-18-crown-6 (bpmdc), with hydrated transition metal perchlorate salts resulted in 2D networks with the composition [M(H2O)2(Hbpmdc)2](ClO4)4·xH2O (M2+ = Ni, x = 4 (1); Cu, x = 2 (2) and Zn, x = 4 (3)). The addition of sodium thiocyanate led to displacement of the aqua ligands, yielding [M(NCS)2(Hbpmdc)2](ClO4)2·2H2O (M2+ = Fe (4), Ni (5)), as well as a THF containing variant of Fe (6). A five-coordinate, copper-containing 2D network, [Cu(NCS)(bpmdc)2](NCS) (7), was isolated in the case of copper, while zinc proved to be the exception to the 2D coordination polymer motif, yielding a 1D chain motif [Zn(NCS)2(bpmdc)2] (8). Across these structures the dipyridylazacrown ether ligand showed a remarkably consistent adoption of the S-configuration when empty or singly protonated with a water guest, with bridging lengths varying by only 1.3 A. The magnetic behaviour of the Fe2+ network 4 was investigated and the d6 compound was found to remain high spin at all temperatures between 300 and 2 K, and thus did not show spin-crossover behaviour.

Monitoring the stepwise assembly of a 3-D framework from a supramolecular lanthanoid synthon by in situ infrared spectroscopy

Construction of a 3-D supramolecular network from [Ln(cpb)(3)(H(2)O)(2)] (Ln = Nd, Tb; Hcpb = 1-(4-cyanophenyl)-1,3-butanedione) by sequential displacement of a coordinated water by DMF, dimerisation by reciprocal hydrogen bonding in solution and pi-pi stacking and interdigitation of nitriles has been monitored by in situ fourier transform infrared spectroscopy.