Energy Barrier Enhancement by Ligand Substitution in Tetrairon(III) Single Molecule Magnets

A dramatic increase of the energy barrier (Ueff) in tetrairon(III) single-mol. magnets can be achieved by simple chem. modification. Site-specific replacement of the six methoxide bridges in [Fe4(OMe)6(dpm)6] (Hdpm = dipivaloylmethane; Ueff/kB = 3.5 K) with two tripodal 1,1,1-tris(hydroxymethyl)ethane (H3thme) ligands affords [Fe4(thme)2(dpm)6] with Ueff/kB = 15.6(2) K and a magnetic relaxation time exceeding 1000 s at T <0.2 K. The prepd. complex is trigonal, space group R-3c, Z = 6, R1 = 0.0370, R2 = 0.1089

A Tetracopper(II) Complex Containing Two \u3bc-Oxamidato-dicopper(II) Units Linked by Croconate Anions

Crystals of the title compd., di-\u3bc-croconato-bis{\u3bc-[N,N'-bis(3-amino-2,2-dimethylpropyl)oxamidato(2-)-N,O':N',O]dicopper(II)} tetrahydrate, are triclinic, space group P-1, with a 9.496(1), b 10.6620(8), c 12.966(2) \uc5, \u3b1 71.481(8), \u3b2 75.780(10), \u3b3 66.160(10)\ub0; Z = 1, dc = 1.647, dm = 1.65(1); R = 0.032, Rw(F2) = 0.087 for 6246 reflections. The structure comprises two \u3bc-oxamidato-dicopper(II) units bridged by croconate ligands to give a tetracopper(II) ring system with crystallog. -1 symmetry; all the Cu centers are five-coordinate

The bonding of thiazoles to platinum(II) complexes. X-ray crystal structure of cis- and trans-[Pt(dimethyl sulfoxide)(thiazole)Cl-2]

The crystal structures of neutral cis- and trans-[Pt(dimethylsulfoxide)(thiazole)Cl2] have been determined by X-ray diffraction. The longer C4-C5 bond distance of the N-coordinated thiazole in both the square planar complexes, as compared to the free ligand, is interpreted in terms of a negative charge density transfer toward the antibonding orbital system of the thiazolic ring

Synthesis, Crystal and Molecular Structure, and Spectroscopic Characterization of 5\u2013(1\u2013Hydroxycyclohexylthio)\u20131,3,4\u2013thiadiazole\u20132\u2013thione

2,5-Dimercapto-1,3,4-thiadiazole (DMTDA), when dissolved in cyclohexanone, interacts strongly with the solvent and the title monothiohemiacetal (MTH) is formed. MTH has been characterized in the solid state by means of X-ray diffraction, IR spectroscopy and thermogravimetric analysis, and in cyclohexanone solution by means of NMR spectroscopy. The title compound crystallizes in the triclinic space group P-1 (No. 2), with cell dimensions a = 6.481 (1), b = 9.322(1), c = 9.553(1) angstrom, alpha = 72.31 (1), beta = 89.74(1), gamma = 80.83(1)\ub0 and Z = 2. The structure was solved by direct methods and least-squares refinement of structural parameters led to a conventional R factor of 0.041 for 1074 independent reflections. In the solid state, MTH easily undergoes decomposition with loss of cyclohexanone

Structure of catena\u2013(2\u2013Amino\u20131,3,4\u2013Thiadiazolium, 2\u2013Amino\u20131,3,4\u2013Thiadiazole bis(mu\u2013Iodo)\u2013di\u2013Iodo\u2013Bismuth(III))

[(C2H4N3S) (C2H3N3S) BiI4]infinity; [(HL) (L) BiI4]infinity (L = 2-amino-1,3,4-thiadiazole), M(r) = 919.86, monoclinic, P 1 2(1)/a 1, a = 7.622(1), b = 18.977(2), c = 12.821(1)angstrom, beta = 102.77(1)-degrees, final R = 0.033. The crystals consist of HL+ cations, neutral L molecules and polymeric [BiI4]infinity- anions built up of edge-sharing [BiI6]3- octahedra, with Bi-I(bridging) distances in the range 3.320(1)-3.057(1) angstrom and Bi-I(terminal) distances in the range 2.917(1)-2.929(1)angstrom. The H-1 and C-13 spectra in DMSO-d6 solution are used in conjunction with the X-Ray structural results to establish the preferred protonation site of the thiadiazole ring

Structure and Magnetic Properties of a Decanuclear Oxoiron(III) Cluster: A Further Step to Understanding Iron Aggregation Processes

[Fe10O4(OMe)16(dbm)6]·xCHCl3 (1) was prepd. and characterized by x-ray crystallog. The crystal lattice contains decairon clusters and highly disordered chloroform mols. The temp. dependence of the magnetic susceptibility of 1 was investigated and the magnetic behavior was indicative of strong antiferromagnetic interactions

Synthesis, Crystal and Molecular Structure, and Infrared Characterization of Two Amino Derivatives of 1,3,4–Thiadiazole

2-Amino-5-methyl-1,3,4-thiadiazole, 2-amino-5-methyl-3H-1,3,4-thiadiazolium bromide [(amtzH)(amtz)Br] and bis(2,5-diamino-3H-1,3,4-thiadiazolium) sulfate [(a2tzH)2SO4] were prepd. and characterized by x-ray structural anal. and IR spectroscopy. The crystals of (amtzH)(amtz)Br are monoclinic. Its asym. unit contains one protonated amtzH cation, one neutral amtz mol., and one bromide ion. The crystals of (a2tzH)2SO4 are monoclinic. The structure is built up of one crystallog. independent a2tzH cation and one half sulfate ion with crystallog. dictated twofold symmetry

Structure and Magnetic Properties of a Dodecanuclear Twisted-ring Iron(III) Cluster

[Fe(OMe)2(dbm)]12 (I; Hdbm = dibenzoylmethane) was prepd. by the reaction of FeCl3 with Hdbm in presence of KOMe or CsOMe in anhyd. MeOH. I.6CHCl3 is monoclinic, space group P21/c, Z = 4, R = 0.0967, Rw = 0.3174. Each Fe(III) in I has a distorted octahedral environment with 6 O atoms from methoxide and dbm with Fe-O band lengths of 1.94-2.07 Å, forming a twisted ring which is not planar and has C1 point group symmetry. NMR data of I in presence of NaBPh4 or LiBPh4 indicate that I is quant. converted to hexairon(III) coronates, [MFe6(OMe)12(dbm)6]+. Magnetic susceptibility data indicate antiferromagnetic coupling in I between high-spin Fe(III) atoms