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A series of cyclometalated iridium(III) complexes with either 4-(2-pyridyl)-1,2,3-triazole or 1-(2-picolyl)-1,2,3-triazole ancillary ligands to give complexes with either 5- or 6-membered chelate rings were synthesized and characterized by a combination of X-ray crystallography, electron spin ionization-high-resolution mass spectroscopy (ESI-HRMS), and nuclear magnetic resonance (NMR) spectroscopy. The electronic properties of the complexes were probed using absorption and emission spectroscopy, as well as cyclic voltammetry. The relative stability of the complexes formed from each ligand class was measured, and their excited-state properties were compared. The emissive properties are, with the exception of complexes that contain a nitroaromatic substituent, insensitive to functionalization of the ancillary pyridyl-1,2,3-triazole ligand but tuning of the emission maxima was possible by modification of the cyclometalating ligands. It is possible to prepare a wide range of optimally substituted pyridyl-1,2,3-triazoles using copper Cu(I)-catalyzed azide alkyne cycloaddition, which is a commonly used "click" reaction, and this family of ligands represent an useful alternative to bipyridine ligands for the preparation of luminescent iridium(III) complexes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aliphatic linkage has relatively little effect on coordination geometry around Zn(II). [•] Aliphatic linkage has a significant effect on the crystal structure. [•] Zn(II) forms five- and six-coordinated complexes with N4O2 and N4S2 Schiff bases. [•] The terminal pyrrolic nitrogens participate as anionic nirogens in complexation. [•] Zn–Npyrrole bonds are relatively stronger than to Zn–Nimine bonds. [Copyright &y& Elsevier]

Graphical abstract Three new coordination compounds fabricated from Cd(NO 3) 2 ·4H 2 O and a helical organic ligand benzilbis((pyridin-2-yl)methylidenehydrazone (L) in the presence of two equivalents of NaHal 2 (Hal = Cl, Br, I) in a mixture of MeOH and EtOH, namely [CdCl 2 L]·1.5MeOH (1), [CdBr 2 L]·EtOH (2) and [CdI 2 L] (3). Hirshfeld surface analysis showed that the structures of 1 – 3 are highly dominated by H⋯X (X = H, C and Hal) contacts. In the diffuse reflectance spectra, 1 – 3 each exhibit bands almost exclusively in the UV region up to about 450 nm, and the band gap energies were estimated to be 2.92, 3.03 and 3.11 eV, respectively. Highlights • We report three Cd(II) complexes from benzilbis((pyridin-2-yl)methylidenehydrazone. • All the structures are stabilized by intermolecular H-bonding and C–H⋯π interactions. • The optical properties of 1 – 3 have been studied by diffuse reflectance spectroscopy. • 1 – 3 each exhibit bands almost exclusively in the UV region up to about 450 nm. Abstract We report design and structural characterization of three new coordination compounds fabricated from Cd(NO 3) 2 ·4H 2 O and a helical organic ligand benzilbis((pyridin-2-yl)methylidenehydrazone (L) in the presence of two equivalents of NaHal (Hal = Cl, Br, I) in a mixture of MeOH and EtOH, namely [CdCl 2 L]·1.5MeOH (1), [CdBr 2 L]·EtOH (2) and [CdI 2 L] (3). The synthesis and design strategy involved using a branched tube, where temperature differential led to slow crystallization of the compounds. The ligand L is bound via two pyridyl-imine units with a tetradentate coordination mode yielding the 12π electron chelate ring. All the structures are stabilized by intermolecular hydrogen bonding and C–H⋯π interactions. Hirshfeld surface analysis showed that the structures of all the complexes are highly dominated by H⋯X (X = H, C and Hal) contacts. The optical properties of 1 – 3 have been investigated by diffuse reflectance spectroscopy. 1 – 3 each exhibit bands almost exclusively in the UV region up to about 450 nm, and the band gap energies were estimated to be 2.92, 3.03 and 3.11 eV, respectively. [ABSTRACT FROM AUTHOR]

We synthesized a tridentate Schiff base ligand, 6‐(((2‐hydroxyphenyl)amino)methylene)‐2‐methoxycyclohexa‐2,4‐dienone [H2L], as well as its Mo(VI) complex [MoO2(L)(DMSO)], and then characterized them completely using elemental analysis, FT‐IR, UV–Vis and 1HNMR spectroscopy techniques. X‐ray single crystal diffraction method was used for the determination of the structure of the synthesized ligand and complex. All other spectroscopic techniques performed, confirmed that [MoO2(L)(DMSO)]had an octahedral geometry around the Mo(VI) central ion coordinated by the donor atoms of the deprotonated ligand, two oxido groups and one oxygen atom of DMSO molecule. Hybrid functional B3LYP with DGDZVP as basis set was applied for DFT calculations of the compounds in their ground state. The MEP, Mulliken, HOMO‐LUMO energy gap and thermodynamic properties of the compounds were also theoretically predicted. In‐vitro antimicrobial studies on the synthesized compounds indicated the great antibacterial activities of the Mo(VI) complex against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus cereus bacteria. [ABSTRACT FROM AUTHOR]

We have reported the synthesis and physical and chemical studies of the new zinc complexes of N(4)-substituted bis(thiosemicarbazones). The complexes characterized by spectroscopic methods. The crystal structures of the compounds [Zn 2 L2 (CH 3 COO)]·EtOH and [Zn 2 L4 (CH 3 COO)]·MeOH is determined. Bis(thiosemicarbazones) involving a pendant OH group having SNONS donor sequences can hold two metal ions in close proximity. The coordination sphere has been formed by the imine nitrogen and sulfur atom, and the remaining positions, in a square-based pyramid, has been occupied by three oxygen atoms derived of pendant OH, ether group and acetate ligand. Acetate ligand and alkoxide oxygen are bridged between two metal centers. Whereas, their non-hydroxyl analogues are dimer. In dimer complexes, two ligands are tetradentate coordinated via N 2 S 2 donor atoms. The presence of bulky groups on the nitrogens of thiosemicarbazide enforce an s-trans conformation for the H 2 L1 and H 2 L3 ligands in [Zn L1 ] 2 ·MeOH and [Zn L3 ] 2 ·MeOH. Fluorescence studies suggest that the [Zn L1 ] 2 ·MeOH complex can be utilized as a fluorescent imaging agent. [ABSTRACT FROM AUTHOR]

Asymmetric, potentially tetradentate ligands ( H 2 L5 , H 2 L6 · 2MeOH ) are formed by subsequent condensation a 4-chlorophenyl thiosemicarbazide and 4-phenyl thiosemicarbazide for H 2 L5 , 4-chlorophenyl thiosemicarbazide and 4-bromophenyl thiosemicarbazide for H 2 L6 · 2MeOH on dialdehyde (1). The mixed bis(thiosemicarbazones) and their copper(II) and nickel(II) complexes have been characterized with 1 HNMR, IR, electronic spectra and X-ray crystallography. Both bis(thiosemicarbazones) form square-planar N 2 S 2 complexes with nickel(II) and copper(II). Electrochemical investigation showed that all Cu(II) and Ni(II) complexes were reducible. The differences observed in the electrochemistry between symmetric and asymmetric complexes cannot be explained only by considering the electronic and steric effects of the substituents, it seems that the arrangement of energy levels of molecular orbitals has been changed in converting a symmetric into an asymmetric structure. The redox potential of asymmetric complexes has been shifted toward more positive potentials compared to the symmetric compounds. [ABSTRACT FROM AUTHOR]

Three cadmium(II) coordination polymers, namely {[Cd(HLI)(NO3)2]·0.5MeOH}n (1), {[Cd(HLII)(NO3)2]·EtOH}n (2), and [Cd2(LII)2(NO3)2]n (3), have been self-assembled from Cd(NO3)2 and N,N′,O-pincer-type isonicotinoylhydrazone-based ditopic ligands (HLI = N′-(pyridin-2-ylmethylene)isonicotinohydrazide and HLII = N′-(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide) and have been characterized experimentally and by DFT computations. In compounds 1 and 2, the corresponding ligand is coordinated to the metal center in the keto form and acted as a tetradentate chelating–bridging agent in which the nitrogen atom of the 4-pyridine ring is coordinated to the cadmium center of the neighboring unit, yielding 1D zig-zag coordination polymers. In compound 3, the ligand was singly-deprotonated and is coordinated in the enolic form with the nitrate ion further acted as a bridging agent, yielding a 2D network. It is revealed by the extended transition state natural orbital for chemical valence (ETS-NOCV) charge and energy decomposition scheme that typical hydrogen bonds O–H⋯O and N–H⋯O, which constitute the networks of 1 and 2, though dominated by a classic Coulomb term, are characterized by an equally important London dispersion constituent due to extra π⋯π and C–H⋯X contacts (X = O, H–C, H–N). The architecture of 3 is due to ionic and dative-covalent Cd–X (X = N, O) bonds as well as London dispersion-driven homopolar dihydrogen C–H⋯H–C and C–H⋯O interactions. NOCV-based representation allowed us to determine that hydrogen bonds O–H⋯O are twice weaker than the corresponding N–H⋯O in the networks of 1 and 2. [ABSTRACT FROM AUTHOR]

The reaction of MoVIO2(L-NS2) [L-NS2 = 2,6-bis(2,2-diphenyl-2-thioethyl)pyridinate(2-)] or MoV2O3(L-NS2)2 with excess PPh3 in N,N-dimethylformamide at 70 °C results in the formation of gray-green (L-NOS)MoIV(¼-O)((¼-S)MoIV(L-NS2) [L-NOS = 2(¼(2,2-diphenyl-2-thioethyl)-6-(2,2-diphenyl-2-oxoethyl)pyridinate(2-)] (1). The crystal structure of 1 revealed a dinuclear complex comprised of two trigonal bipyramidal Mo centers bridged along an axial-equatorial edge (the ¼-O-(¼-S vector) such that the MoN bonds are trans to the bridging atoms and are anti with respect to the MoMo bond (d(MoMo) = 2.5535(5) Å); the remaining coordination sites are occupied by the S- and O-donor atoms of the L-NOS and L-NS2 ligands. The diamond core is asymmetric, with Mo(1/2)-O(1) distances of 1.845(2) and 2.009(2) Å and Mo(1/2)-S(1) distances of 2.374(1) and 2.230(1) Å. Compound 1 is unique in possessing a planar, diamond-core unit devoid of terminal oxo ligation and a new tridentate L-NOS ligand formed via a novel intramolecular modification of the original L-NS2 ligand. [ABSTRACT FROM AUTHOR]

A variant of 1,4,7,10-tetraazacyclododecane (cyclen) bearing two semicarbazone pendant groups has been prepared. The octadentate ligand forms complexes with Bi3+ and Pb2+. X-ray crystallography showed that the neutral ligand provides an eight-coordinate environment for both metal ions and intermolecular hydrogen bond interactions have influenced the coordination environments of both complexes in the solid state. NMR spectroscopy revealed a fluxional environment for both complexes. The ligand was radiolabeled with the α-emitting radioactive isotope 213Bi3+, which is used in systemic targeted radiotherapy. The resulting complex was stable in serum for at least 90 min (two decay half-lives). The Pb2+ complex has reasonably fast kinetics of formation (t1/2 = 20 min) at 25 °C and pH 7.4. The Bi3+ and Pb2+ complexes show kinetic stability in 1.2 M HCl (half-lives of 214 min and 47 min, respectively). This is the first description of a macrocycle bearing semicarbazone pendant groups and its utility in coordinating main group metals, specifically those with radiotherapeutic potential. [ABSTRACT FROM AUTHOR]

The positron‐emitting radionuclide, fluorine‐18, is used to radiolabel molecules to develop tracers for diagnostic imaging with positron‐emission tomography. There is growing interest in the potential of using strong coordinate bonds between electropositive Ga(III) and electronegative fluoride (≈ 557 kJ/mol) to provide new methods of incorporating fluorine‐18 into molecules. The potential of gallium(III) complexes with acyclic pentadentate bispicolinic acid containing ligands (H2L1–3) to form ternary complexes with fluoride, [GaL1–3F] was investigated with a view to developing new methods for fluorine‐18 radiolabelling. A solid‐phase peptide synthesis approach was used to produce a bispicolinic acid chelator with a lysine residue. Characterisation of [GaL1X] (X = OH, Cl, F) by X‐ray crystallography revealed that L1 acted as dianionic N2O2 donor to the Ga(III) with the fifth site occupied by a monodentate anion (OH–, Cl– or F–). Despite its high stability in aqueous mixture and [D6]DMSO and the straightforward synthesis of [GaL1F], it was only possible to form the radioactive analogue [18F][GaL1F] in low radiochemical yields. [ABSTRACT FROM AUTHOR]

The chiral complex Tp*WII{(R)-(+)-NHCH(Me)Ph}(CO) 2 has been synthesized and spectroscopically and structurally characterized. It has the potential to reduce crystallographic disorder upon derivatization and to bolster chiral methodologies in Tp*-W chemistry. • Synthesis of the chiral tungsten Tp* complex Tp*WII{(R)-(+)-NHCH(Me)Ph}(CO) 2. • The characterization of the complex by analytical and spectroscopic techniques. • Determination of a high-quality X-ray crystal structure for the complex. • The complex has the potential to induce crystallographic ordering in derivatives. • The complex has potential for the development of chiral W-Tp* chemistry. Reaction of Tp*WIII(CO) 2 [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate] with (R)-(+)-α-methylbenzylamine [(R)-(+)-LH 2 ] in dichloromethane yields blue, diamagnetic Tp*WII{(R)-(+)-LH}(CO) 2 , which has been characterised by microanalysis, mass spectrometry, infrared, 1H NMR, 13C{1H} NMR and electronic spectroscopies, and X-ray crystallography. The six-coordinate, distorted-octahedral (skew-trapezoidal-bipyramidal) complex is composed of a W(II) center bound to mutually cis carbonyl [C–W–C = 71.1(3)°] and (R)-(+)-LH ligands and a facially tridentate Tp* ligand. The complex is unusually stable and resistant to oxygen- and sulfur-atom transfer reactions directed at the W center. [ABSTRACT FROM AUTHOR]

A new series of five zinc (II) coordination polymers, namely [Zn(LI)(NO 3)(OH 2)] n (1) , [Zn(LI)(CH 3 COO)] n (2) , [Zn(LI)(NCS)] n (3) , [Zn(LII)(CH 3 COO)] n (4) , and {[Zn 2 (LII) 2 (N 3) 2 ] ⋅H 2 O} n (5) , has been self-assembled from different zinc (II) salts and pyridine-hydrazine ligands {HLI = 2-pyridinecarbaldehyde isonicotinoyl hydrazone, and HLII = 2-acetyl-pyridyl-isonicotinoylhydrazone} and has been structurally characterized. In all compounds, the ligand is singly-deprotonated and coordinates to the zinc center in the enolic form (=N–N=C–O-). In other words, the pyridine-hydrazine ligand acted as a tetradentate negatively charged chelating-bridging ligand and coordinated to the metal centers in N, N, O pincer mode and the Para -nitrogen of the pyridine ring coordinated to the zinc center of the adjacent unit. In compounds (1)-(4) the ancillary ligands act as terminal ligands and the zinc centers bridging by the pyridine-hydrazine building blocks formed one-dimensional 1D coordination polymers, whereas the azide N 3 − anion in compound (5) further acted as a bridging agent and led to the formation of two-dimensional 2D network. A detailed analysis of Hirshfeld surfaces and fingerprint plots allows a comparison of intermolecular interactions in (1) – (5) , which are crucial in building supramolecular architectures. A series of five zinc (II) coordination polymers, has been self-assembled from different zinc (II) salts and pyridine-hydrazine ligands. In compounds (1)-(4), the ancillary ligands act as terminal ligands and the zinc centers bridging by the pyridine-hydrazine building blocks formed one-dimensional 1D coordination polymers, whereas the azide N 3 − anion in compound (5) further acted as a bridging agent and led to the formation of two-dimensional 2D network. Image 1 • Five Zn(II) coordination polymers have been synthesized and characterized. • Supramolecular networks have been explored by a single crystal diffraction method. • Hirshfeld surface analysis has been used to evaluate intermolecular interactions. [ABSTRACT FROM AUTHOR]

A new sarcophagine cage amine ligand with a pendent carboxylate functional group has been synthesised; the ligand has been conjugated to tumour targeting peptides ([Tyr3]-octreotate and [Lys3]-bombesin) and the conjugates radiolabelled with copper-64. [ABSTRACT FROM AUTHOR]

Reaction of TpiPrMoVIOS(OAr) with cobaltocene in toluene results in the precipitation of brown, microcrystalline oxosulfido-Mo(V) compounds, [CoCp2][TpiPrMoVOS(OAr)] (Cp- = έ5-C5H5-, TpiPr- = hydrotris(3-isopropylpyrazol-1-yl)borate, OAr- = phenolate or 2-sBu, 2-tBu, 3-tBu, 4-sBu, 4-Ph, 3,5-sBu2, 2-CO2Me, 2-CO2Et or 2-CO2Ph derivative thereof). The compounds are air- and water-sensitive and display ν(Mo-O) and ν(Mo-S) IR absorption bands at ca. 890 and 435 cm-1, respectively, 20-40 cm-1 lower in energy than the corresponding bands in TpiPrMoOS(OAr). They are electrochemically active and exhibit three reversible cyclovoltammetric waves (E(MoVI/MoV) = -0.40 to -0.66 V, E([CoCp2]+/CoCp2) = -0.94 V and E(CoCp2/[CoCp2]-) = -1.88 V vs SCE). Structural characterization of [CoCp2][TpiPrMoOS(OC6H4CO2Et-2)]·2CH2Cl2 revealed a distorted octahedral Mo(V) anion with Mo-O and Mo-S distances of 1.761(5) and 2.215(2) Å, respectively, longer than corresponding distances in related TpiPrMoOS(OAr) compounds. The observation of strong S(1s) → (S(3p) + Mo(4d)) S K-preedge transitions indicative of a d¹ sulfido-Mo(V) moiety and the presence of short Mo-O (ca. 1.72 Å) and Mo-S (ca. 2.25 Å) backscattering contributions in the Mo K-edge EXAFS further support the oxosulfido-Mo(V) formulation. The compounds are EPR-active, exhibiting highly anisotropic (Δg 0.124-0.150), rhombic, frozen-glass spectra with g1 close to the value observed for the free electron (ge = 2.0023). Spectroscopic studies are consistent with the presence of a highly covalent Mo-S π* singly occupied molecular orbital. The compounds are highly reactive, with reactions localized at the terminal sulfido ligand. For example, the compounds react with cyanide and PPh3 to produce thiocyanate and SPPh3, respectively, and various (depending on solvent) oxo-Mo(V) species. Reactions with copper reagents also generally lead to desulfurization and the formation of oxo-Mo(V) or -Mo(IV) complexes. [ABSTRACT FROM AUTHOR]

The article provides information on a study that reported on the synthesis and characterization of the first molybdenum-copper carbon monoxide dehydrogenase complexes. The study stated that a unique heterobimetallic Mo/Cu active site is present in the carbon monoxide dehydrogenase from Oligotropha carboxidovorans. This enzyme catalyzes the oxidation of carbon oxide and carbon dioxide. Some of the experiments done regarding the paramagnetic active site models indicated that few mechanisms invoke the direct participation of the sulfido ligand in the formation of thiocarbonate intermediates.

The synthesis and characterization of a silver complex of the tripodal triazole ligand, tris(benzyltriazolylmethyl)amine (TBTA, L¹), that is used as promoter to enhance CuI-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. X-ray analysis of the silver(I) complex with L¹ reveals a dinuclear cation, [Ag2(L¹)2]2+, that is essentially isostructural to the copper(I) analogue. While the [Ag2(L¹)2](BF4)2 complex provides catalysis for the azide-alkyne cycloaddition process, evidence is presented that this arises from trace copper contamination. The synthesis of silver(I), copper(II), and copper(I) complexes of a second tripodal ligand, tris(2-benzimidazolymethyl)amine (L²), which is used to enhance the rate of CuAAC reactions, is also reported. X-ray crystallography of the CuI complex [Cu3I(L²)2(CH3CN)2](BF4)3 offers structural insight into previous mechanistic speculation about the role of this ligand in the CuAAC reaction. [ABSTRACT FROM AUTHOR]

Compared to tris(2-phenylpyridine)iridium(III) ([Ir(ppy)3]), iridium(III) complexes containing difluorophenylpyridine (df-ppy) and/or an ancillary triazolylpyridine ligand [3-phenyl-1,2,4-triazol-5-ylpyridinato (ptp) or 1-benzyl-1,2,3-triazol-4-ylpyridine (ptb)] exhibit considerable hypsochromic shifts (ca. 25-60 nm), due to the significant stabilising effect of these ligands on the HOMO energy, whilst having relatively little effect on the LUMO. Despite their lower photoluminescence quantum yields compared with [Ir(ppy)3] and [Ir(df-ppy)3], the iridium(III) complexes containing triazolylpyridine ligands gave greater electrogenerated chemiluminescence (ECL) intensities (using tri- n-propylamine (TPA) as a co-reactant), which can in part be ascribed to the more energetically favourable reactions of the oxidised complex (M+) with both TPA and its neutral radical oxidation product. The calculated iridium(III) complex LUMO energies were shown to be a good predictor of the corresponding M+ LUMO energies, and both HOMO and LUMO levels are related to ECL efficiency. The theoretical and experimental data together show that the best strategy for the design of efficient new blue-shifted electrochemiluminophores is to aim to stabilise the HOMO, while only moderately stabilising the LUMO, thereby increasing the energy gap but ensuring favourable thermodynamics and kinetics for the ECL reaction. Of the iridium(III) complexes examined, [Ir(df-ppy)2(ptb)]+ was most attractive as a blue-emitter for ECL detection, featuring a large hypsochromic shift ( λmax=454 and 484 nm), superior co-reactant ECL intensity than the archetypal homoleptic green and blue emitters: [Ir(ppy)3] and [Ir(df-ppy)3] (by over 16-fold and threefold, respectively), and greater solubility in polar solvents. [ABSTRACT FROM AUTHOR]

The use of copper radioisotopes in cancer diagnosis and radionuclide therapy is possible using chelators that are capable of binding CuII with sufficient stability in vivo to provide high tumour-to-background contrast. Here we report the design and synthesis of a new bifunctional chelator, 5-(8-methyl- 3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid (MeCOSar), that forms copper complexes of exceptional stability by virtue of a cage amine (sarcophagine) ligand and a new conjugate referred to as SarTATE, obtained by the conjugation of MeCOSar to the tumour-targeting peptide Tyr3-octreotate. Radiolabeling of SarTATE with 6CuII, a radioisotope suitable for positron emission tomography (PET), was fast (∼20 min), easily performed at room temperature and consistently resulted in high radiochemical purity (>99%). In vitro and in vivo evaluation of 64CuSarTATE demonstrated its high selectivity for tumour cells expressing somatostatin receptor 2 (sstr2). Biodistribution and PET imaging comparisons were made between 64CuSarTATE and 64Cu-labeled DOTA-Tyr3-octreotate (64CuDOTATATE). Both radiopharmaceuticals showed excellent uptake in sstr2-positive tumours at 2 h post-injection. While tumour uptake of 64CuDOTATATE decreased significantly at 24 h, 64CuSarTATE activity was retained, improving contrast at later time points. 64CuSarTATE accumulated less than 64CuDOTATATE in the nontarget organs, liver and lungs. The uptake of 64CuSarTATE in the kidneys was high at 2 h but showed significant clearance by 24 h. The new chemistry and pre-clinical evaluation presented here demonstrates that MeCOSar is a promising bifunctional chelator for Tyr3-octreotate that could be applied to a combined imaging and therapeutic regimen using a combination of 64Cu- and 67CuSarTATE complexes, owing to improved tumour-to-non-target organ ratios compared to 64CuDOTATATE at longer time points. [ABSTRACT FROM AUTHOR]

The synthesis of new cage amine macrobicyclic ligands with pendent carboxylate functional groups designed for application in copper radiopharmaceuticals is described. Reaction of [Cu((NH2)2sar)]2+ (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) with either succinic or glutaric anhydride results in selective acylation of the primary amine atoms of [Cu((NH2)2sar)]2+ to give derivatives with either one or two aliphatic carboxylate functional groups separated from the cage amine framework by either a four- or five-atom linker. The CuII serves to protect the secondary amine nitrogen atoms from acylation, and can be removed to give the free ligands. The newly appended carboxylate functional groups can be used as sites of attachment for cancer-targeting peptides such as Lys3-bombesin. The synthesis of the first dimeric sarcophagine-peptide conjugate, possessing two Lys3-bombesin peptides tethered to a single cage amine, is presented. This species has been radiolabeled with copper-64 at ambient temperature and there is minimal dissociation of CuII from the conjugate even after two days of incubation in human serum. [ABSTRACT FROM AUTHOR]

Sky-blue Tp*WOCl2 has been synthesized from the high-yielding reaction of Tp*WO2Cl with boron trichloride in refluxing toluene. Dark-red Tp*WOI2 was prepared via thermal decarbonylation followed by aerial oxidation of Tp*WI(CO)3 in acetonitrile. From these precursors, an extensive series of mononuclear tungstenyl complexes, Tp*WOXY [X = C-, Y = OPh-, SPh-; X = Y = OPh-, 2-(n-propyl)pheno1ate (PP-), SPh-, SePh; XY = toluene-3,4-dithiolate (tdt2-), quinoxaline-2,3-dithiolate (qdt2-), benzene-1,2-diselenolate (bds2-); Tp* = hydrotris(3,5-dimethylpyrazol-l-yl)borate], was prepared by metathesis with the respective alkali-metal salt of X-/XY2- or (NHEt3)2(qdt). The complexes were characterized by microanalysis, mass spectrometry, electrochemistry, IR, electron paramagnetic resonance (EPR), and electronic absorption spectroscopies, and X-ray crystallography (for X Y = OPh-, PP-, SPh-; XY = bds²). The six-coordinate, distorted-octahedral tungsten centers are coordinated by terminal oxo [W≡O = 1.689(6)-1.704(3) Å], tridentate Tp*, and monodentate or bidentate O/S/Se-donor ligands. Spin Hamiltonian parameters derived from the simulation of fluid-solution X-band EPRspectra revealed that the soft-donor S/Se ligand complexes had largerg values and smaller 183W hyperfine coupling constants than the less covalent hard-donor O/Cl species. The former showed low-energy ligand-to-metal charge-transfer bands in the near-IR region of their electronic absorption spectra. These oxotungsten(V) complexes display lower reduction potentials than their molybdenum counterparts, underscoring the preference of tungsten for higher oxidation states. Furthermore, the protonation of the pyrazine nitrogen atoms of the qdt2- ligand has been examined by spectroelectrochemistry; the product of the one-electron reduction of [Tp*WO(qdtH)]+ revealed usually intense low-energy bands. [ABSTRACT FROM AUTHOR]

Green/blue Tp[sup/Pr]rMoO(S[sub2]PR[sub2]) (Tp[sup/Pr] = hydrotris(3-isopropylpyrazolyl)borate; R Pr[supi], Ph, OEt, OPr[supi], (-)-mentholate) complexes were synthesized and characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopy, and X-ray crystallography. The diamagnetic, six-coordinate, oxo-Mo(IV) complexes possess distorted octahedral geometries defined by terminal oxo, bidentate dithio acid, and tridentate Tp ligands. The R = Pr[supi] and Ph derivatives are isomers of previously reported 1,2-borotropically shifted complexes, Tp[sup/Pr*]MoO(S[sub2]PR[sub2]) (Tp[sup/Pr*] = hydrobis(3-isopropylpyrazolyl)(5-isopropylpyrazolyl)borate; ref: Inorg. Chem. 1996, 35, 5368). Conversion of Tp[sup/Pr]MoO(S2PPh2) into Tp[sup/Pr*]MoO(S[sub2]PPh[sub2]) at elevated temperatures (>80 °C) showed that the borotropically shifted isomer was thermodynamically more stable than the unshifted species. Reaction with methanol converts Tp[sup/Pr]MoO(S[sub2]PPr[supi][sub2]) into (HB(OMe)(Prsupi]pz)[sub2])MoO(S[sub2]PPr[supi]) (Pr[supi]pz = 3-isopropylpyrazolyl), which was characterized by spectroscopic and crystallographic methods. [ABSTRACT FROM AUTHOR]

Atom transfer reactions have been employed to convert Tp/PrMoO2(OAr) into monomeric cis- oxosulfido-Mo(VI) and dimeric y-disulfido-Mo(V) species, [Tp/PrrMoOS(OAr)]n (Tp/Pr = hydrotris(3-isopropyl- pyrazol-1 -yl)borate; OAr = phenolate or naphtholate derivative; n = 1 and 2, respectively). Dark red, monomeric Tp/PrMoOS(OAr) complexes contain distorted octahedral cis-oxosulfido-Mo(VI) centers, with d(Mo=O) = 1.692(5) Å, d(Mo=S) = 2.132(2) Å, and ∠(O=Mo=S) = 103.68(16)° for the 2-sec-butylphenolate derivative. Dark red-purple, dimeric [Tp/PrMoOS(OAr)]2 complexes undergo S–S bond cleavage forming monomeric oxosulfido-Mo(VI) species in solution. In the solid state, the 3,5-di-tert- butylphenolate derivative exhibits a centrosymmetric structure, with distorted octahedral anti oxo-Mo(V) centers bridged by a disulfido-κS,κS' ligand. Hydrolysis of the oxosulfido-Mo(VI) complexes results in the formation of [Tp/PrMoO]2(μ-S2)(μ-O). In anaerobic solutions, certain oxosulfido-Mo(Vl) complexes convert to molybdenyl complexes bearing bidentate 2-mercaptophenolate or related naphtholate ligands formed via intramolecular attack of the sulfido ligand on a coligand C-H group. The oxosulfido-Mo(Vl) complexes serve as precursors to biologically relevant Mo(V) and heterobimetallic MoO(μ-S)Cu species and undergo a range of biomimetic reactions. [ABSTRACT FROM AUTHOR]

The first member of a water-soluble family of bis(thiosemiCarbazone) ligands is reported. It forms a 1:1 complex with Zn" that absorbs intensely in the visible region (λmax) = 414 nm; ϵ 1.8(4) x M-1 cm-1; pH 7.3). Its affinity for Znll (KD = 5.9(3) x 10-9 M at pH 7.3) was determined by competition with ligand ethylene glycol O,σ-bis(2-aminoelhyl)-N,N,M,N'-tetraacetic acid. Its potential application as a chromophoric probe was demonstrated by estimation of the Znll binding affinities of the soluble metal-binding domains of two plant metal-transporting proteins. [ABSTRACT FROM AUTHOR]

The synthesis of four new water-soluble bis(thiosemicarbazone) ligands and their copper(ii) complexes is presented and their potential to be new ligands for copper radiopharmaceuticals is discussed. The ligands and complexes have been characterized by a combination of NMR spectroscopy, mass spectrometry, and X-ray crystallography. The electrochemical behaviour of two of the copper(ii) complexes was investigated by cyclic voltammetry and revealed that both complexes exhibited a quasi-reversible redox process attributed to a CuII/CuI process. Two of the new ligands were radiolabelled with positron-emitting 64Cu with a view to assessing their potential as ligands that bind radioactive copper isotopes for application in diagnostic radiopharmaceuticals. The cellular uptake of the copper complexes was investigated in SH-SY5Y cells. [ABSTRACT FROM AUTHOR]