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Linkage Isomers (linkage + isomer)

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Chemistry100%

Selected Abstracts

ChemInform Abstract: Photogeneration of Nitrosyl Linkage Isomers in Octahedrally Coordinated Platinum Complexes in the Red Spectral Range.

CHEMINFORM, Issue 20 2010
Dominik Schaniel
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr7Ni, Cr6Ni2, and Cr7Ni2 Rings Templated About Imidazolium Cations

CHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009
Angelika
Abstract The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4-DiMe-ImidH][Cr7NiIIF8(O2CtBu)16] 1 (2,4-DiMe-ImidH=the cation of 2,4-dimethylimidazole), [ImidH]2[Cr6NiII2F8(O2CCtBu)16] 2 (ImidH=the cation of imidazole), and [1-Bz-ImidH]2 [Cr7NiII2F9(O2CtBu)18] 3 (1-Bz-ImidH=the cation of 1-benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3. In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X-ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J,,5.8,cm,1, and it is not possible to differentiate the exchange between two CrIII centers (JCrCr) from the exchange between a CrIII and a NiII center (JCrNi). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present. [source]

Reactions of [Et4N][Tp*W(,3 -S)(,-S)2­(CuSCN)2] with Nitrogen Donor Ligands: Syntheses, Structures, and Third-Order Nonlinear Optical Properties

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2009
Zhen-Hong Wei
Abstract Reactions of the preformed cluster [Et4N][Tp*W(,3 -S)(,-S)2(CuSCN)2] (1) with pyridine (py), 4,4,-bipyridine (4,4,-bipy), or 1,3-bis(4-pyridyl)propane (bpp) led to the formation of three neutral [Tp*W(,3 -S)(,-S)2Cu2]-based compounds [Tp*W(,3 -S)(,-S)2Cu2(SCN)(py)2] (2), [{Tp*W(,3 -S)(,-S)2Cu2(SCN)}2(4,4,-bipy)]·3.5H2O (3·3.5H2O), and [Tp*W(,3 -S)(,-S)2Cu2(SCN)(bpp)]2 (4), respectively. Compounds 2,4 were characterized by elemental analysis, IR spectra, UV/Vis spectra, 1H NMR, and X-ray analysis. There are two linkage isomers [Tp*W(,3 -S)(,-S)2Cu2(SCN)(py)2] and [Tp*W(,3 -S)(,-S)2Cu2(NCS)(py)2], each of which has its own enantiomeric pair in the crystal of 2. Compound 3 has a double butterfly-shaped structure in which two [Tp*W(,3 -S)(,-S)2Cu2(SCN)] fragments are linked with a single 4,4,-bipy bridge. For 4, the two butterfly-shaped [Tp*W(,3 -S)(,-S)2Cu2(SCN)] fragments are interconnected by a pair of bpp bridges. The third-order nonlinear optical (NLO) performances of 2,4 in DMF were also investigated by Z -scan techniques.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Linkage isomeric oxamate chelates: rac -bis(ethane-1,2-diamine)oxamatocobalt(III) bis(trifluoromethanesulfonate) dihydrate and ,(+)578 -bis(ethane-1,2-diamine)[oxamato(2,)]cobalt(III) trifluoromethanesulfonate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009
Anders Hammershøi
The structures of rac -bis(ethane-1,2-diamine)(oxamato-,2O1,O2)cobalt(III) bis(trifluoromethanesulfonate) dihydrate, [Co(C2H2NO3)(C2H8N2)2](CF3SO3)2·2H2O, (I), and ,(+)578 -bis(ethane-1,2-diamine)[oxamato(2,)-,2N,O1]cobalt(III) trifluoromethanesulfonate, [Co(C2HNO3)(C2H8N2)2]CF3SO3, (II), are compared. Together, the two complexes constitute the first pair of linkage isomers of bidentate oxamate available for structural comparison. [source]

Linkage isomerism of organoplatinum(II) compounds coordinated by two 1,3-di­methyl­barbiturate anions

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2000
Kishie Noguchi
In two linkage isomers, bis[1,3-di­methyl-2,4,6(1H,3H,5H)-pyrimidine­trionato]- C5,O4 -(ethyl­enedi­amine- N,N,)platinum(II), [Pt(C6H7N2O3)2(C2H8N2)], (I), and bis[1,3-di­methyl-2,4,6(1H,3H,5H)-py­rim­idine­tri­on­ato- C5](ethyl­enediamine- N,N,)­plati­num(II) di­hyd­rate, [Pt(C6H7N2O3)2(C2H8N2)]·2H2O, (II), crystal­lized from the same aqueous solution containing [Pt(en)(OH)2] and 1,3-di­methyl­barbituric acid (Hdmbarb) in a 1:2 molar ratio, a pair of monodentate dmbarb, anions coordinate to the Pt atom at tetrahedral C atoms for (II), while one dmbarb, anion coordinates at the carbon and the other at a deprotonated enol oxy­gen for (I). The Pt,C distances in (I) and (II) are comparable: 2.112,(4),Å for (I), and 2.114,(4) and 2.117,(4),Å for (II). [source]

Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr7Ni, Cr6Ni2, and Cr7Ni2 Rings Templated About Imidazolium Cations

CHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009
Angelika
Abstract The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4-DiMe-ImidH][Cr7NiIIF8(O2CtBu)16] 1 (2,4-DiMe-ImidH=the cation of 2,4-dimethylimidazole), [ImidH]2[Cr6NiII2F8(O2CCtBu)16] 2 (ImidH=the cation of imidazole), and [1-Bz-ImidH]2 [Cr7NiII2F9(O2CtBu)18] 3 (1-Bz-ImidH=the cation of 1-benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3. In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X-ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J,,5.8,cm,1, and it is not possible to differentiate the exchange between two CrIII centers (JCrCr) from the exchange between a CrIII and a NiII center (JCrNi). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present. [source]

Heteropolynuclear Palladium Complexes with Pyrazolate and Its 3- tert -Butyl Derivatives: The Effect of Heterometal Ions on the Rate of Isomerization

CHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2006
Keisuke Umakoshi Prof. Dr.
Abstract The heteropolynuclear complexes [Pd2M,2(,-pz)6] (M,=Ag (1), Au (2); pzH=pyrazole), HT -[Pd2M,2(,-3- tBupz)6] (M,=Ag (3,a), Au (4,a); 3- tBupzH=3- tert -butylpyrazole), and HH -[Pd2Au2(,-3- tBupz)6] (4,b) have been prepared and some of them were structurally characterized. When 3- tert -butylpyrazolate was employed as a bridging ligand, two linkage isomers (head-to-tail (HT) and head-to-head (HH)) arise from the difference in orientation of the substituent groups on the pyrazolate bridges between the two Pd atoms. 1H NMR spectroscopy has been used to identify and to follow the reversible stereochemical rearrangement of the HH isomer of [Pd2Ag2(,-3- tBupz)6] (3,b) to form the HT isomer 3,a in CDCl3 and the HT isomer of [Pd2Au2(,-3- tBupz)6] (4,a) to form the HH isomer 4,b in C6D6. Kinetic studies of the reaction have established the rate law to be ,d(HH)/dt=d(HT)/dt=k2[HH],k1[HT] for 3,b and ,d(HT)/dt=d(HH)/dt=k1[HT],k2[HH] for 4,a, where k1 and k2 denote the rate of isomerization from the HT to the HH isomer and that from the HH to the HT isomer, respectively. For typical runs at 50,°C in C6D6, k1=13.8×10,5 s,1, k2=18.6×10,5 s,1, and Keq=k2/k1=1.24 for 3,b, and k1=1.26×10,5 s,1, k2=3.52×10,5 s,1, and Keq=k1/k2=0.36 for 4,a. Temperature-dependent rate measurements reveal ,H, and ,S, to be 100(1) kJ,mol,1 and 0(3) J,mol,1,K,1 for 3,b and 112(5) kJ,mol,1 and 20(17) J,mol,1,K,1 for 4,a, respectively. The rate of isomerization is essentially unaffected by the concentration of the complex or by the presence of neutral bridging ligands. These data and observations imply that the isomerization involves an intramolecular exchange process. [source]

Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis(thiocyanato)(2,2,-bipyridyl)platinum(II)

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2007
Xiao-Ying Hu
Abstract This paper presents a Density Functional or Time Dependent Density Functional (DFT/TDDFT) study of the molecular and electronic structures, optical absorption and emission spectra of three linkage isomers:bis(isothiocyanato-S)(2,2,-bipyridyl) platinum(II) ([Pt(SCN)2(bpy)]), (isothiocyanato-S)(thiocyanato-N)-(2,2,-bipy- ridyl) platinum(II) ([Pt(SCN)(NCS)(bpy)]), and bis(thiocyanato-N)(2,2,)-bipyridyl)platinum(II) ([Pt(NCS)2(bpy)]), in which different coordination ligands based on the N- and S-coordination of the thiocyanato ligands control the luminescent color. The electronic structures were studied using the B3LYP functional. Optimized geometries were compared to the experimentally observed structures. TDDFT calculation was carried out to investigate the excited singlet and triplet states. Calculations have been performed both in vacuo and in solvents, using a polarized continuum model (PCM) to account for solute-solvent interactions. Inclusion of the solvent led to a significant energy change, and as a consequence, the computed spectrum calculated in the presence of the solvent was in good agreement with the experimental determinations. The first two absorptions were found to originate from mixed platinum-SCN (or NSC) to bipyridyl-,* transitions rather than pure metal-to-ligand-charge-transfer (MLCT) transitions, whereas the higher-energy bands arose from intraligand ,,,* transitions. The stretching frequencies of C,N have been calculated both in the ground and excited states, which are relative to the charge transition during the excitation. In addition, different sizes of basis sets were also discussed in this paper. [source]