[closo-B10H8-1-CN-10-Azinium]- Anions: Photoactive Heteroditopic Ligands for Metal Complexes

A new class of rigid, photoactive heteroditopic anionic ligands based on the 1,10-disubstituted [closo-B10H10]2- anion was designed and six of these compounds were obtained from [closo-B10H10]2- in three steps with yields in the range of 25-30%. The design includes two apical substituents, a metal coordinating cyano group and an azinium (4-cyanopyridinium, 4,4'-bipyridinium, pyrazinium, pyrimidinium, and pyridazinium), which provides a secondary binding site. The azinium substituent is involved in an efficient intramolecular charge transfer process and compensates one of the two delocalized negative charges of the boron cluster. The compounds exhibit intramolecular CT bands with maxima in the range of 340-410 nm (MeCN) and two are weakly fluorescent with significant Stokes shifts. A highly colored bis-zwitterionic byproduct with two clusters, [closo-1-CN-B10H8-10-(pyrazinium-1,4-diyl)-10'-B10H8-1'-CN-closo]2-, was also obtained in a low yield. The ligands were structurally characterized (XRD) and their geometrical and photophysical properties were compared to those of the analogues lacking the CN group and the parent pyridinium derivative. A comparative analysis of experimental data was augmented with DFT and TD-DFT results. Two of the ligands (with the 4,4'-bipyridinium and pyrazinium) were converted to (η5-Cp)(dppe)Fe complexes and one of them was used to obtain a heterodinuclear complex with Cu(pdc)(H2O)3 to demonstrate the ditopic function of the ligand. All three iron complexes were characterized by the XRD method.

A Reversible Phase Transition of 2D Coordination Layers by B-H∙∙∙Cu(II) Interactions in a Coordination Polymer

Materials that combine flexibility and open metal sites are crucial for myriad applications. In this article, we report a 2D coordination polymer (CP) assembled from CuII ions and a flexible meta-carborane-based linker [Cu₂(L1)₂(Solv)₂]•xSolv (1-DMA, 1-DMF, and 1-MeOH; L1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane). 1-DMF undergoes an unusual example of reversible phase transition on solvent treatment (i.e., MeOH and CH₂Cl₂). Solvent exchange, followed by thermal activation provided a new porous phase that exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 301 m² g^-1 and is capable of a CO₂ uptake of 41 cm³ g^-1. The transformation is reversible and 1-DMF is reformed on addition of DMF to the porous phase. We provide evidence for the reversible process being the result of the formation/cleavage of weak but attractive B-H∙∙∙Cu interactions by a combination of single-crystal (SCXRD), powder (PXRD) X-ray diffraction, Raman spectroscopy, and DFT calculations.

The key to controlling the morphologies of quantum nanocrystals: spherical carborane ligands

Carboranyl ligands with different functional moieties have been used to obtain different morphologies in the quantum regime using a colloidal route.

All inorganic coordination polymers have been made possible with the m-carboranylphosphinate ligand

New examples of 1D coordination polymers (CPs) and complexes containing the purely inorganic carboranylphosphinate ligand [1-OPH(O)-1,7-closo-C2B10H11]- are reported. The reaction of Na[1-OPH(O)-1,7-closo-C2B10H11] salt with MCl2 (M = Mn, Co, Ni, Cu, Zn and Cd) in MeOH or EtOH leads to compounds 1-8. All compounds have been exhaustively characterized by analytical and spectroscopic techniques. X-ray analysis and spectroscopy characterization revealed the differences between the isolated compounds: 1D polymeric chains (CPs) with carboranylphosphinate ligand bridges have been obtained with MnII, CdII or ZnII centres, whereas compounds with low nuclearity have been isolated with CuII, CoII and NiII. No polymeric structures were obtained in the CoII and NiII complexes due to the higher affinity of these metals for water than that for the m-carboranylphosphinate and accordingly, these complexes generate supramolecular hydrophobic/hydrophilic structures. The reactivity of manganese polymer 1 with water leads to the breakage of the polymer with the formation of a new mononuclear compound 2, and that in methanol leads back to the initial polymer 1. However, the reactivity of polymer 1 with 2,2'-bpy maintains the core present in the initial polymer, leading to the CP 3, which in methanol/water medium produces species of lower nuclearity. The magnetic properties of the compounds studied show weak antiferromagnetic coupling.

Controllable assembly of Cu(ii) coordination compounds based on a flexible zwitterionic benzimidazole–dicarboxylate ligand: synthesis, structural diversity, reversible SCSC transformation and magnetic properties

The reversible SCSC transformation of a paddle-wheel cluster to a 1D linear polymer could be accomplished.

Carborane-layered double hydroxide nanohybrids for potential targeted- and magnetically targeted-BNCT applications

Carborane-intercalated layered double hydroxide nanohybrids (CB-LDH) and a magnesium ferrite (MF) supported-CB-LDH core–shell nanocomposite (CB-LDH@MF) are reported.

Carving a 1D CoII-carboranylcarboxylate system by using organic solvents to create stable trinuclear molecular analogues: complete structural and magnetic studies

An unprecedented strategy for the synthesis of a 1D Co^II carboranylcarboxylate polymer and their linear trinuclear derivatives.

Synthesis and reactions of N-heterocycle functionalised variants of heterometallic {Cr7Ni} rings

Here we present a series of linked cage complexes of functionalised variants of the octametallic ring {Cr₇Ni} with the general formula [ⁿPr₂NH₂][Cr₇NiF₈(O₂C^tBu)₁₅(O₂CR)], where HO₂CR is a N-heterocycle containing carboxylic acid.

Hetero-bimetallic paddlewheel clusters in coordination polymers formed by a water-induced single-crystal-to-single-crystal transformation

Hetero-bimetallic paddlewheel clusters in coordination polymers are formed through a water-induced single-crystal to single-crystal transformation.

Intramolecular hydrogen bonding stabilizes the nuclearity of complexes. A comparative study based on the H-carborane and Me-carborane framework

The H– on the adjacent carbon of the carboranylcarboxylate ligand is responsible for intramolecular interactions that stabilize the nuclearity of Cu(ii) complexes.

Homochiral coordination cages assembled from dinuclear paddlewheel nodes and enantiopure ditopic ligands: syntheses, structures and catalysis

A series of homochiral (Cu₂)₂L₄ lantern cages have been synthesized, which can promote cyclopropanation with up to 99 : 1 diastereoselectivity.

Carba-closo-dodecaborate anions with two functional groups: [1-R-12-HC≡C-closo-1-CB₁₁H₁₀]⁻ (R = CN, NC, CO₂H, C(O)NH₂, NHC(O)H)

Disubstituted carba-closo-dodecaborate anions with one functional group bonded to the cluster carbon atom and one ethynyl group bonded to the antipodal boron atom were synthesized from easily accessible {closo-1-CB11} clusters. [Et4N][1-NC-12-HC≡C-closo-1-CB11H10] ([Et4N]4b) was prepared starting from Cs[12-Et3SiC≡C-closo-1-CB11H11] (Cs1c) via salts of the anions [1-HO(O)C-12-HC≡C-closo-1-CB11H10](-) (2b) and [1-H2N(O)C-12-HC≡C-closo-1-CB11H10](-) (3b). In a similar reaction sequence [Et4N][1-CN-12-HC≡C-closo-1-CB11H10] ([Et4N]7b) was obtained from Cs[1-H2N-12-HC≡C-closo-1-CB11H10] (Cs5b) by formamidation to yield [Et4N][1-H(O)CHN-12-HC≡C-closo-1-CB11H10] ([Et4N]6b) and successive dehydration. In addition, the synthesis of the isonitrile [Et4N][1-CN-closo-1-CB11H11] ([Et4N]7a) is presented. The {closo-1-CB11} derivatives were characterized by multinuclear NMR as well as vibrational spectroscopy, mass spectrometry, and elemental analysis. The crystal structures of [Et4N][1-HO(O)C-12-HC≡C-closo-1-CB11H10] ([Et4N]2b), [Et4N][1-H2N(O)C-12-HC≡C-closo-1-CB11H10] ([Et4N]3b), [Et4N][1-NC-12-HC≡C-closo-1-CB11H10] ([Et4N]4b), [Et4N][1-H(O)CHN-12-HC≡C-closo-1-CB11H10] ([Et4N]6b), [Et4N][1-CN-12-HC≡C-closo-1-CB11H10] ([Et4N]7b), and K[1-H(O)CHN-closo-1-CB11H11] ([Et4N]6a) were determined. The transmission of electronic effects through the carba-closo-dodecaboron cage was studied based on (13)C NMR spectroscopic data, by results derived from density functional theory calculations, and by a comparison to the data of related benzene and bicyclo[2.2.2]octane derivatives.

Dinuclear copper complexes: coordination of Group 14 heteroborates

The dinuclear copper(i) complex [Cu₂(μ-dmapm)(CH₃CN)₂][BF₄]₂ was reacted with Group 14 heteroborates. Four different coordination motives have been characterized.