Synthesis, Structural Characterization, and Host-Guest Studies of Aminoquinonato-Bridged Re(I) Supramolecular Rectangles.

Aminoquinonato bridged Re(I)-based metallarectangles have been constructed via an orthogonal bonding approach. Self-assembly of Re2(CO)10 and aminoquinone ligands in the presence of ditopic linear pyridyl ligands has resulted in the formation of metallarectangles of the general formula [{(CO)3Re(µ-η(4)-L)Re(CO)3}2(µ-N-L'-N)2] (1-4), wherein 1, L = 2,5-bis(n-butylamino)-1,4-benzoquinonato (bbbq) and N-L'-N = 4,4'-bipyridine (bpy); 2, L = 2,5-bis(phenethylamino)-1,4-benzoquinonato (bpbq) and N-L'-N = 4,4'-bipyridine; 3, L = 2,5-bis(n-butylamino)-1,4-benzoquinonato (bbbq) and N-L'-N = trans-1,2-bis(4-pyridyl)ethylene (bpe) and 4, L = 2,5-bis(phenethylamino)-1,4-benzoquinonato (bpbq) and N-L'-N = trans-1,2-bis(4-pyridyl)ethylene (bpe). Metallarectangles 1-4 have been characterized by elemental analysis, IR, NMR, and UV-vis absorption spectroscopic techniques. The molecular structures of 1 and 4 were determined by single-crystal X-ray diffraction methods. The molecular recognition capability of 1 and 3 with pyrene and triphenylene has been investigated using UV-vis absorption and emission spectroscopic techniques. The formation of host-guest complex has been further corroborated by the single-crystal X-ray structural evidence of carceplex system (3⊃pyrene)·(DMF).

Self-assembly of oxamidato bridged ester functionalised dirhenium metallastirrups: synthesis, characterisation and cytotoxicity studies.

A new set of ester functionalised Re(i)-based oxamidato bridged neutral dinuclear metallacycles were synthesised by self-assembly of four components from three building blocks in a facile one-pot reaction via an orthogonal bonding approach. Oxidative addition of oxamide ligands (H2L = N,N'-diphenyloxamide, and N,N'-dibenzyloxamide) to rhenium carbonyl (Re2(CO)10) in the presence of semi-rigid and flexible ditopic pyridyl ligands (L' = o-phenylene diisonicotinate (pdi), ethane diyl di-4-pyridine carboxylate (etdp) and 1,4-butane diyl di-4-pyridine carboxylate (budp)) having ester functionality afforded neutral dirhenium metallacycles of the general formula [(CO)3Re(µ-L)(µ-L')Re(CO)3] (1-5) under solvothermal reaction conditions. The metallacyclic compounds were characterised using elemental analyses, IR, UV-vis and NMR spectroscopic techniques. Structural analyses of 2-5 by single crystal X-ray diffraction methods revealed a stirrup like molecular framework in which two fac-Re(CO)3 units are bridged together by dissymmetrical NO∩ON bis-chelation of oxamide ligands (as a pedestal of stirrups) and further connected by a flexible ditopic tecton (as an arched anchor of stirrups) in an orthogonal fashion. The cytotoxicity activities of dirhenium metallacycles 1-5 were studied in vitro against three different cancer cell lines and normal cells.

Self-assembly of a fac-Mn(CO)3-core containing dinuclear metallacycles using flexible ditopic linkers.

Syntheses of manganese(i)-based dinuclear metallacycles have been accomplished under facile one-pot reaction conditions at room temperature. Self-assembly of four components has resulted in the formation of M2L2-type metallacycles [Mn(CO)3Br(µ-NLN)]2 (1-5) using pentacarbonylbromomanganese as the metal precursor and flexible ligands such as 1,2-bis(4-pyridyl)ethane (bpa), 1,2-bis(4-pyridyl)propane (bpp), 1,2-ethanediyl di-4-pyridine carboxylate (edp), 1,4-butanediyl di-4-pyridine carboxylate (budp), and 1,6-hexanediyl di-4-pyridine carboxylate (hedp) as linkers. The metallacycles have been characterized on the basis of IR, NMR, UV-vis, and ESI-mass spectroscopic techniques and single-crystal X-ray diffraction methods. The host capability of the metallacycles has been demonstrated using single-crystal X-ray crystallography.

Self-assembly of Thiolato-Bridged Manganese(I)-Based Metallarectangles: One-pot Synthesis and Structural Characterization.

A new series of thiolato-bridged manganese(I)-based supramolecular rectangles have been achieved by three-precursor self-assembly of Mn2(CO)10, diaryl disulfides (RSSR), and linear ditopic azine ligands (L) [L = pyrazine (pz), 4,4'-bipyridine (bpy), and trans-1,2-bis(4-pyridyl)ethylene (bpe)] using a one-pot synthetic strategy. Oxidative addition of RSSR (diphenyl disulfide and p-tolyl disulfide) to manganese decacarbonyl in the presence of rigid bidentate ligands (L) afforded metallarectangles of the general formula [{(CO)3Mn(µ-SR)2Mn(CO)3}2(µ-L)2] (1-6). Compounds 1-6 were characterized using elemental analyses and NMR, IR, and UV-vis absorption spectroscopic techniques. The molecular structures of metallarectangles 1, 3, and 5 were elucidated by single-crystal X-ray diffraction methods. The guest binding ability of 3 and 5 has been investigated with two aromatic guests using electronic absorption and fluorescence emission spectroscopy, and the results revealed a strong binding interaction between host-guest species.

One-pot synthesis of oxamidato-bridged hexarhenium trigonal prisms adorned with ester functionality.

Oxamidato-bridged Re(I)-based hexanuclear trigonal prisms with ester functionality have been synthesised via a multicomponent self-assembly process under solvothermal conditions. The self-assembly of Re2(CO)10, oxamide ligands (H2L1 = N,N'-dibutyloxamide, H2L2 = N,N'-dioctyloxamide, H2L3 = N,N'-didodecyloxamide and H2L4 = N,N'-dibenzyloxamide) and phenyl-1,3,5-tris(isonicotinate) (ptin) resulted in the formation of metallaprisms with the general formula [{(CO)3Re(µ­Î·(4)-L)Re(CO)3}3(µ3-ptin)2] (1­4). The metallaprisms 1­4 have been characterised using spectroscopic techniques, and the molecular structure of 4 has been elucidated by single-crystal X-ray diffraction methods. Investigations on the guest binding ability of 2 with a few aromatic alcohols and L-tryptophan using UV­vis and fluorescence spectroscopic titration experiments revealed strong host­guest interactions. The luminescence enhancement studies of 2 and 3 have been carried out using organic-aqueous solvent mixtures.