ORCID Profile
0000-0002-3305-852X
Current Organisation
Purdue University
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Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1DT11237F
Abstract: Two lanthanide tetrafluoro-p-phthalate (L(2-)) complexes, Ln(L)(1.5)·DMF·H(2)O (Ln = Pr(3+) (1), Nd(3+) (2)), were synthesized using pyridine as a base. The compounds were found to be isostructural, and the structure of 1 has been determined by single crystal X-ray diffraction (monoclinic, space group C2, a = 22.194(2) Å, b = 11.4347(12) Å, c = 11.7160(12) Å, β = 94.703(2)°, V = 2963.3(5) Å(3), Z = 4). The crystal structure of 1 consists of dinuclear Pr(3+) units, which are connected by tetrafluoro-p-phthalate, forming separate 2D polymeric layers. The Ln(3+) ions in the dinuclear Ln(2) units are linked by two μ-O atoms and by two bridging O-C-O groups. The structure is porous with DMF and water molecules located between layers. Non-coordinated DMF molecules occupy about 27% of the unit cell volume. A systematic analysis of reported structures of Ln(III) polymers with p-phthalate and its derivatives shows that the ca. known 60 structures can be ided into six possible structural types depending on the presence of certain structural motifs. The magnetic properties of compounds 1 and 2 were studied. The dependence of χ(M)T on T (where χ(M) is magnetic susceptibility per dinuclear lanthanide unit) for 1 and 2 was simulated using two different models, based on: (i) the Hamiltonian Ĥ = ΔĴ(z)(2)+ μ(B)g(J)HĴ, which utilises an axial splitting parameter Δ and temperature-independent paramagnetism (tip) and (ii) crystal field splitting. It was found that both models gave satisfactory fits, indicating that the Ln-Ln exchange interactions are small and the symmetry of the coordination environment is the main factor influencing the magnetic properties of these compounds.
Publisher: International Union of Crystallography (IUCr)
Date: 15-02-2022
DOI: 10.1107/S2056989022001220
Abstract: Syntheses are described for the blue urple complexes of cobalt(II) chloride with the tetradentate ligands 1,4-bis[2-(pyridin-2-yl)ethyl]piperazine (Ppz), 1,4-bis[2-(pyridin-2-yl)ethyl]homopiperazine (Phpz), trans -2,5-dimethyl-1,4-bis[2-(pyridin-2-yl)ethyl]piperazine (Pdmpz) and tridentate 4-methyl-1-[2-(pyridin-2-yl)ethyl]homopiperazine (Pmhpz). The CoCl 2 complexes with Ppz, namely, {μ-1,4-bis[2-(pyridin-2-yl)ethyl]piperazine}bis[dichloridocobalt(II)], [Co 2 Cl 4 (C 18 H 24 N 4 )] or Co 2 (Ppz)Cl 4 , and Pdmpz (structure not reported as X-ray quality crystals were not obtained), are shown to be dinuclear, with the ligands bridging the two tetrahedrally coordinated CoCl 2 units. Co 2 (Ppz)Cl 4 and {dichlorido{4-methyl-1-[2-(pyridin-2-yl)ethyl]-1,4-diazacycloheptane}cobalt(II) [CoCl 2 (C 13 H 21 N 3 )] or Co(Pmhpz)Cl 2 , crystallize in the monoclinic space group P 2 1 / n , while crystals of the pentacoordinate monochloro chelate 1,4-bis[2-(pyridin-2-yl)ethyl]piperazine}chloridocobalt(II) perchlorate, [CoCl(C 18 H 24 N 4 )]ClO 4 or [Co(Ppz)Cl]ClO 4 , are also monoclinic ( P 2 1 ). The complex {1,4-bis[2-(pyridin-2-yl)ethyl]-1,4-diazacycloheptane}dichloridocobalt(II) [CoCl 2 (C 19 H 26 N 4 )] or Co(Phpz)Cl 2 ( P \\overline{1}) is mononuclear, with a pentacoordinated Co II ion, and entails a Phpz ligand acting in a tridentate fashion, with one of the pyridyl moieties dangling and non-coordinated its displacement by Cl − is attributed to the solvophobicity of Cl − toward MeOH. The pentacoordinate Co atoms in Co(Phpz)Cl 2 , [Co(Ppz)Cl] + and Co(Pmhpz)Cl 2 have substantial trigonal–bipyramidal character in their stereochemistry. Visible- and near-infrared-region electronic spectra are used to differentiate the two types of coordination spheres. TDDFT calculations suggest that the visible/NIR region transitions contain contributions from MLCT and LMCT character, as well as their expected d–d nature. For Co(Pmhpz)Cl 2 and Co(Phpz)Cl 2 , variable-temperature magnetic susceptibility data were obtained, and the observed decreases in moment with decreasing temperature were modelled with a zero-field-splitting approach, the D values being +28 and +39 cm −1 , respectively, with the S = 1/2 state at lower energy.
Publisher: American Chemical Society (ACS)
Date: 14-01-2014
DOI: 10.1021/IC401928M
Abstract: Reactions of the copper(II)-gadolinium(III) 15-metallacrown-5 complex [GdCu5(Glyha)5(NO3)2(H2O)6](NO3) (Glyha(2-) = dianion of glycinehydroxamic acid) with different di/tricarboxylates (1,3-phthalate, 1,4-phthalate, biphenyl-4,4'-dicarboxylate, citrate) resulted in formation of different types of products: {[(GdCu5(Glyha)5(H2O)2)(GdCu5(Glyha)5(H2O)3)(1,3-bdc)3]·16H2O}n (1), {[(GdCu5(Glyha)5(H2O)3)2(1,4-bdc)2](1,4-bdc)·8H2O}n (2), {[(GdCu5(Glyha)5(H2O)4)2(1,4-bdc)3]·8H2O}n (3), [GdCu5(Glyha)5(Citr)(H2O)4]·7H2O (4), {[GdCu5(Glyha)5(H2O)5](μ2-CO3)[Cu(Fgg)]}·7H2O (5) and [Cu(Gly)2(H2O)]n (6) (where bdc(2-) is the corresponding phthalate (benzenedicarboxylate), Citr(3-) is citrate, Fgg(3-) is the trianion of [(N-formylaminoacetyl)amino]acetic acid and Gly(-) is glycinate). Complexes 1-5 contain the [GdCu5(Glyha)5](3+) cation. Complexes 2 and 3 possess the same composition but differ by the mode of p-phthalate coordination to the [GdCu5(Glyha)5](3+) unit. In compounds 1-3, metallacrown cations are linked by the corresponding phthalates in 1D, 1D and 2D polymers, respectively, whereas 4 and 5 are discrete molecules. Compound 5 is the product of a multistep reaction, which finally involves atmospheric CO2 capture. Hydrolysis of hydroxamate in this reaction is confirmed by isolation of a mononuclear copper glycine complex 6. The χMT vs T data for 1 were fitted using a model based on the Hamiltonian Ĥ (GdCu5) = -2J1(S1 × SGd + S2 × SGd + S3 × SGd + S4 × SGd + S5 × SGd) - 2J2(S1 × S2 + S2 × S3 + S3 × S4 + S4 × S1 + S5 × S1. The best fit corresponded to J1 = +0.60(2) cm(-1), J2 = -61.0(5) cm(-1) and zJ' = -0.035(4) cm(-1). Complex 1 is the first ex le of a 15-metallacrown-5 system, for which numerical values of exchange parameters have been reported. The isotherm for methanol absorption by compound 1 at 293 K was typical for microporous sorbents, whereas ethanol sorption was negligibly small.
Publisher: Elsevier BV
Date: 04-2014
Publisher: International Union of Crystallography (IUCr)
Date: 18-11-2021
DOI: 10.1107/S2056989021011907
Abstract: The core of the title complex, bis[hexaaquahemiaquapentakis(μ 3 -glycinehydroxamato)sulfatopentacopper(II)terbium(III)] sulfate hexahydrate, [TbCu 5 (SO 4 )(GlyHA) 5 (H 2 O) 6.5 ] 2 (SO 4 )·6H 2 O ( 1 ), which belongs to the 15-metallacrown-5 family, consists of five glycinehydroxamate dianions (GlyHA 2− C 2 H 4 N 2 O 2 ) and five copper(II) ions linked together forming a metallamacrocyclic moiety. The terbium(III) ion is connected to the centre of the metallamacrocycle through five hydroxamate oxygen atoms. The coordination environment of the Tb 3+ ion is completed to an octacoordination level by oxygen atoms of a bidentate sulfate and an apically coordinated water molecule, while the copper(II) atoms are square-planar, penta- or hexacoordinate due to the apical coordination of water molecules. Continuous shape calculations indicate that the coordination polyhedron of the Tb 3+ ion in 1 is best described as square antiprismatic. The positive charge of each pair of [TbCu 5 (GlyHA) 5 (H 2 O) 6.5 (SO 4 )] 2 2+ fragments is compensated by a non-coordinated sulfate anion, which is located on an inversion center with 1:1 disordered oxygen atoms. Complex 1 is isomorphous with the previously reported compounds [ Ln Cu 5 (GlyHA) 5 (SO 4 )(H 2 O) 6.5 ] 2 (SO 4 ), where Ln III = Pr, Nd, Sm, Eu, Gd, Dy and Ho.
Publisher: Wiley
Date: 26-09-2011
Publisher: American Chemical Society (ACS)
Date: 06-02-2013
DOI: 10.1021/IC302448D
Abstract: We report highly active iridium precatalysts, [Cp*Ir(N,N)Cl]Cl (1-4), for water oxidation that are supported by recently designed dihydroxybipyridine (dhbp) ligands. These ligands can readily be deprotonated in situ to alter the electronic properties at the metal thus, these catalyst precursors have switchable properties that are pH-dependent. The pKa values in water of the iridium complexes are 4.6(1) and 4.4(2) with (N,N) = 6,6'-dhbp and 4,4'-dhbp, respectively, as measured by UV-vis spectroscopy. For homogeneous water oxidation catalysis, the sacrificial oxidant NaIO4 was found to be superior (relative to CAN) and allowed for catalysis to occur at higher pH values. With NaIO4 as the oxidant at pH 5.6, water oxidation occurred most rapidly with (N,N) = 4,4'-dhbp, and activity decreased in the order 4,4'-dhbp (3) > 6,6'-dhbp (2) ≫ 4,4'-dimethoxybipyridine (4) > bipy (1). Furthermore, initial rate studies at pH 3-6 showed that the rate enhancement with dhbp complexes at high pH is due to ligand deprotonation rather than the pH alone accelerating water oxidation. Thus, the protic groups in dhbp improve the catalytic activity by tuning the complexes' electronic properties upon deprotonation. Mechanistic studies show that the rate law is first-order in an iridium precatalyst, and dynamic light scattering studies indicate that catalysis appears to be homogeneous. It appears that a higher pH facilitates oxidation of precatalysts 2 and 3 and their [B(Ar(F))4](-) salt analogues 5 and 6. Both 2 and 5 were crystallographically characterized.
Publisher: International Union of Crystallography (IUCr)
Date: 29-06-2011
Publisher: Elsevier BV
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 07-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2DT31121F
Abstract: Six homodinuclear and two heteronuclear complexes Tp(Np)Co-C(2)O(4)-CoTp(Np) (1), Tp(Np)Co-C(2)O(4)-NiTp(Cy) (2), Tp(Cy)Ni-C(2)O(4)-NiTp(Cy) (3), Tp(Np)Co-C(2)O(2)(NH)(2)-CoTp(Np) (4), Tp(Cy)Ni-C(2)O(2)(NH)(2)-NiTp(Cy) (5), Tp(Np)Co-C(2)S(2)(NH)(2)-CoTp(Np) (6), Tp(Np)Co-C(2)S(2)(NH)(2)-NiTp(Cy) (7), Tp(Cy)Ni-C(2)S(2)(NH)(2)-NiTp(Cy) (8) (Tp(Np) = tris(3-neopentylpyrazolyl)borate, Tp(Cy) = tris(3-cyclohexylpyrazolyl)borate), were synthesized and characterized by mass spectrometry, electronic spectroscopy and X-ray crystallography. These compounds possess similar molecular structures, with the metal ions linked by bridging oxalate (1-3), oxamidate (4 and 5) or dithiooxamidate (6-8) ions. The heteronuclear nature of compounds 2 and 7 was additionally confirmed by high-resolution mass spectrometry. The magnetic properties of the Co(2+) complexes were modelled taking into account zero-field splitting of this ion, yielding D-values for Co(2+) in the range -17(1) to -50(1) cm(-1). All the metal ion pairs in compounds 1-8 are antiferromagnetically-coupled, with J values between -10.0(1) and -45.0(2) cm(-1) (via the exchange Hamiltonian Ĥ(ex.) = -2JŜ(1)Ŝ(2)) and |J| increasing in the order oxalate < oxamidate < dithiooxamidate. This tendency can be attributed to greater M-S bond covalency compared to M-N or M-O bonds (M = Co(2+) and Ni(2+)). It was found that this antiferromagnetic coupling of Co(2+) and Ni(2+) ions through oxalate is more efficient for these tris(pyrazolyl)borate complexes than for similar oxalate-bridged systems with neutral aliphatic amine ligands.
Publisher: Elsevier BV
Date: 06-2020
Publisher: Wiley
Date: 10-08-2018
Publisher: Wiley
Date: 07-09-2010
Publisher: Wiley
Date: 15-05-2008
Location: United States of America
No related grants have been discovered for Matthias Zeller.