Synthesis of cis-p-dioxano-12-crown-4 and X-ray crystallography of the (1:1) complex with lithium thiocyanate

The synthesis of a novel 12-crown-4 analogue (cis-p-dioxano-12-crown-4 or cis-3,6,9,13,15-pentaoxabicyclo[9.3.1]pentadecane) is described. The (1:1) LiNCS complex crystallizes in the monoclinic Cc space group; a = 8.4973(2) Å, b = 18.0659(4) Å, c = 8.9168(1) Å, and β = 90.713(1)° with Z = 4. The crown adopts C1 symmetry to which the Li+ is coordinated in a rectangular pyramid with an apical NCS

(Terpyridine)palladium(II) complexes of phenylcyanamide ligands

(Terpyridine)palladium(II) complexes of phenylcyanamide anion ligands have been prepared and characterized by UV-vis, IR, and 1H-NMR spectroscopies. A crystal structure determination of the complex [Pd(terpy)(2,6-Cl2-pcyd)] [PF6] has been performed. The overall geometry of the complex is approximately planar with a dihedral angle of 2.16(16)∘ between the best plane fit of the palladium coordination sphere and that for the phenyl ring of the phenylcyanamide ligand. Crystal structure data for the complex: C22H14N5Cl2PF6Pd, monoclinic crystal system and space group P21/n, with a = 8.185(5) Å, b = 13.606(7) Å, c = 21.163(5) Å,β = 90.50(3)∘, V= 2356.8(20) Å−3, and Z = 4. The structure was refined by using 3233 Mo Kα reflections with I > 2.5σ(I) to an R factor of 0.034. The UV-vis spectra of the complexes showed a broad band centered at approximately 400 nm which has been assigned to a πnb → σ* LMCT transition of the Pd(II)-NCN chromophore

(1,3-Bis(2′-pyridylimino)isoindolinato)nickel(II) complexes of phenylcyanamido ligands: crystal structure, electronic absorption spectroscopy and solvent adduct studies

Complexes of the formula Ni(L)X, where L=1,3-bis(2′-pyridylimino)isoindolinato and X=Cl, Br, N3, NCS, 2-Clpcyd, 4-Clpcyd, 2,3-Cl2pcyd,2,6-Cl2pcyd, 2,4,5-Cl3pcyd and 2,3,5,6-Cl4pcyd, have been synthesized and characterized by elemental analysis, and IR, 1H NMR and UVVis spectroscopies. A crystal structure determination of Ni(L)(2-Clpcyd) showed nickel in a distorted square planar coordination sphere of nitrogen donor atoms in which the phenylcyanamido ligand is coordinated to Ni(II) via the terminal nitrogen. The solvent coordination equilibria of Ni(L)(pcyd) complexes was also investigated and the results suggest that both electronic and steric factors play important roles in determining the stability of the solvated complex

1H dynamic NMR and x-ray crystal structure studies of conformational preferences in dibenzo [c,h] [1,6] diazecines

The conformational equilibria and preferences in dibenzo[c,h] [1,6]diazecines have been investigated by 1H DNMR measurements and X-ray crystallography. It has been found that restricted rotation about the exocyclic N-S bond in 6,13-ditosyl-6,7,13,14-tetrahydro-5H,12H-dibenzo[c,h][1,6] diazecine 2 becomes slow on the NMR timescale in the temperature range 200-300 K. The free energy of activation was determined to be 43.5 ± 0.5 kJ mol-1 for this dynamic process. Steric hindrance at the transition state is deemed to be the most important contribution to the N,S barrier. From X-ray crystal structure analyses, it appears that the influence of the N-inversion on this barrier is negligible. The conformation in the solid state is also the preferred one in solution. The X-ray structure illustrates the spatial vicinity of the tosyl groups relative to the annelated benzene moieties of the 10-membered ring. Consistent with these results are high field shifts and corresponding splittings in the aromatic part of the 1H NMR spectrum of compound 2

A pentaammineruthenium(III) dimer with the novel bridging ligand 4,4′-dicyanamidobiphenyl dianion

The novel ligand 4,4′-dicyanamidobiphenyl dianion (bp2-) has been synthesized and characterized by 13C NMR spectroscopy, cyclic voltammetry, and crystallography. The crystal structure of [Ph4As]2[bp]·H2O showed that bp2- is approximately planar with a dihedral angle of 8.2° between phenyl ring planes and the cyanamide groups in an ami conformation. The water of crystallization is asymmetrically hydrogen bonded between cyanamide groups of adjacent bp2- ions. The crystal data for C62H48N4As2+H2O are monoclinic crystal system and space group P21/c with a = 12.998(5) Å, b = 13.465(4) Å, c = 28.703(13) Å, β = 98.94(3)°, V = 4963(3) Å3, and Z = 4. The structure was refined by using 4555 reflections with I > 2.5σ(I) to an R factor of 0.058. The complex, [{(NH3}5Ru}2(μ-bp)][X]4, where X = tosylate or PF6 - ions, was also synthesized and characterized by 1H NMR spectroscopy, cyclic voltammetry, spectroelectrochemistry, and temperature-dependent magnetic susceptibility measurements. From cyclic voltammetry measurements, the comproportionation constants to form the mixed-valence complex [{(NH3}5Ru)2(μ-bp)]3+ were estimated to be 4.1, 16, and 22 in water, acetonitrile, and nitromethane, respectively. The trend and magnitude of Kc suggests solvent valence trapping of a weakly coupled Class II ion. The MMCT band of the mixed-valence complex had to be deconvoluted from the low-energy LMCT band and had the following properties in acetonitrile, νmax = 8400 cm-1, εmax = 3300 M-1 cm-1, and Δν1/2 = 3300 cm-1. The weak superexchange mediating properties of bp2- compared to 1,4-dicyanamidobenzene dianion were suggested to arise from the

Synthesis and characterization of 123I-CMICE-013: A potential SPECT myocardial perfusion imaging agent

Coronary artery disease (CAD) is a major cause of death in Canada and the United States. Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a useful diagnostic test in the management of patients with CAD. The widely used SPECT MPI agents, 99mTc sestamibi and 99mTc tetrofosmin, exhibit less than ideal pharmacokinetic properties with decreasing uptake with higher flows. 123I has a similar energy as 99mTc, an ideal half life, and is readily available from cyclotrons. The objective of this study was to develop an 123I labeled MPI agent based on rotenone, a mitochondrial complex I inhibitor, as an alternative to currently available SPECT MPI agents. Methods: 123I-CMICE-013 was synthesized by radiolabeling rotenone with 123I in trifluoroacetic acid (TFA) with iodogen as the oxidizing agent at 60 C for 45 min, followed by RP-HPLC purification. The product was formulated in 5% EtOH in 10 mM NaOAc pH 6.5. The inactive analog 127I-CMICE-013 was isolated and characterized by NMR and mass spectrometry, and the structure determined. Micro-SPECT imaging studies were carried out in normal and infarcted rats. Biodistribution studies were performed in normal rats at 2 h (n = 6) and 24 h (n = 8) post injection (p.i.). Results: 123I-CMICE-013 was isolated with >95% radiochemical purity and high specific activity (14.8-111 GBq/μmol; 400-3000 mCi/μmol). Structural analysis showed that rotenone was iodinated at 7′-position, with removal of the 6′,7′-double bond, and addition of a hydroxy group at 6′-position. MicroSPECT images in normal rats demonstrated homogeneous and sustained myocardial uptake with minimal interference from lung and liver. Absent myocardial perfusion was clearly identified in rats with permanent left coronary artery ligation and ischemia-reperfusion injury. In vivo biodistribution studies in normal rats at 2 h p.i. showed significan