Novel Topologies in Vanadium-bis-ß-Diketone Chemistry: A [V4] and a [V6] Metallacyclophane

Exploring the chemistry of vanadyl ions (VO2+) with bis-ß-diketone ligands, in pyridine reactions of vanadyl sulfate with 1, 3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-benzene (H4L1) and 1, 3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, (VIVO)4(H2L1)4(py)4] (1) and (VVO)4(VIVO)2 (O)4(L2)2(py)6] (2) were prepared and characterized. Due to the conformational flexibility of the ligands, both entities exhibit very peculiar metal topologies and composition, differing significantly from structural patterns established in the related chemistry of divalent 3d metals. Structural analysis also unveils the existence of the most complex metallamacrocycles from this family to date. Studies of the magnetic properties via bulk magnetization measurements and EPR spectroscopy confirmed the existence of uncoupled long-distant S = 1/2 metal centers and the spin ground states S = 2 and S = 1 of the clusters

Novel topologies in vanadium-bis-ß-diketone chemistry: a [V4] and a [V6] metallacyclophane

Exploring the chemistry of vanadyl ions (VO2+) with bis-β-diketone ligands, in pyridine reactions of vanadyl sulfate with 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)- benzene (H4L1) and 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, [(VIVO)4(H2L1)4(py)4] (1) and [(VVO)4(VIVO)2 (O)4(L2)2(py)6] (2) were prepared and characterized. Due to the conformational flexibility of the ligands, both entities exhibit very peculiar metal topologies and composition, differing significantly from structural patterns established in the related chemistry of divalent 3d metals. Structural analysis also unveils the existence of the most complex metallamacrocycles from this family to date. Studies of the magnetic properties via bulk magnetization measurements and EPR spectroscopy confirmed the existence of uncoupled long-distant S = 1/2 metal centers and the spin ground states S = 2 and S = 1 of the clusters.Guillem Aromí thanks the Generalitat de Catalunya for the prize ICREA Academia 2008 and 2013, for excellence in research and the ERC (European Research Council) for a Starting Grant (258060 FuncMolQIP). The authors thank the Spanish MICINN for funding through CTQ2009-06959 (Guillem Aromí, Ivana Borilovic) and MAT2011-24284 (Olivier Roubeau). Ivana Borilovic thanks the Generalitat de Catalunya for a Ph.D. Grant (FI-DGR 2014).We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).Peer Reviewe

Accessing Sodium Ferrate complexes containing neutral and anionic N-heterocyclic carbene ligands : structural, synthetic, and magnetic insights

This study reports the synthesis and single-crystal X-ray crystallographic, NMR spectroscopic, and magnetic characterization of a series of sodium ferrates using bis(amide) Fe(HMDS)2 as a precursor (HMDS = 1,1,1,3,3,3-hexamethyldisilazide). Reaction with sodium reagents NaHMDS and NaCH2SiMe3 in hexane afforded donor-solvent-free sodium ferrates [{NaFe(HMDS)3}∞] (1) and [{NaFe(HMDS)2(CH2SiMe3)}∞] (2), respectively, which exhibit contacted ion pair structures, giving rise to new polymeric chain arrangements made up of a combination of inter- and intramolecular Na···Me(HMDS) electrostatic interactions. Addition of the unsaturated NHC IPr (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) to 1 and 2 caused deaggregation of their polymeric structures to form discrete NHC-stabilized solvent-separated ion pairs [Na(IPr)2]+[Fe(HMDS)3]- (3) and [(THF)3·NaIPr]+[Fe(HMDS)2CH2SiMe3]- (4), where in both cases, the NHC ligand coordinates preferentially to Na. In contrast, when IPr is sequentially reacted with the single-metal reagents NaCH2SiMe3 and Fe(HMDS)2, the novel heteroleptic ferrate (THF)3Na[:C{[N(2,6-iPr2C6H3)]2CHCFe(HMDS)2}] (5) is obtained. This contains an anionic NHC ligand acting as an unsymmetrical bridge between the two metals, coordinating through its abnormal C4 position to Fe and its normal C2 position to Na. The formation of 5 can be described as an indirect ferration process where IPr is first metalated at the C4 position by the polar sodium alkyl reagent, which in turn undergoes transmetalation to the more electronegative Fe(HMDS)2 fragment. Treatment of 5 with 1 molar equiv of methyl triflate (MeOTf) led to the isolation and structural elucidation of the neutral abnormal NHC (aNHC) tricoordinate iron complex [CH3C{[N(2,6-iPr2C6H3)]2CHCFe(HMDS)2}] (6) with the subsequent elimination of NaOTf, disclosing the selectivity of complex 5 to react with this electrophile via its C2 position, leaving its Fe-C4 and Fe-N bonds intact. The magnetic susceptibility properties of compounds 1-6 have been examined. This study revealed a drastic change of magnetic susceptibility in replacing a pure σ donor from an idealized trigonal coordination environment by an NHC π donating character

Tandem Mn-I Exchange and Homocoupling Processes Mediated by a Synergistically Operative Lithium Manganate

Pairing lithium and manganese(II) to form lithium manganate [Li2Mn(CH2SiMe3)4] enables the efficient direct Mn-I exchange of aryliodides, affording transient (aryl)lithium manganate intermediates which in turn undergo spontaneous C@C homocoupling at room temperature to furnish symmetrical (bis)aryls in good yields under mild reaction conditions. The combination of EPR with X-ray crystallographic studies has revealed the mixed Li/Mn constitution of the organometallic intermediates involved in these reactions, including the homocoupling step which had previously been thought to occur via a single-metal Mn aryl species. These studies show Li and Mn working together in a synergistic manner to facilitate both the Mn-I exchange and the C@C bond-forming steps. Both steps are carefully synchronized, with the concomitant generation of the alkyliodide ICH2SiMe3 during the Mn-I exchange being essential to the aryl homocoupling process, wherein it serves as an in situ generated oxidant

Novel Topologies in Vanadium-bis-β-Diketone Chemistry: A [V4] and a [V6] Metallacyclophane

Exploring the chemistry of vanadyl ions (VO2+) with bis-β-diketone ligands, in pyridine reactions of vanadyl sulfate with 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-benzene (H4L1) and 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, [(VIVO)4(H2L1)4(py)4] (1) and [(VVO)4(VIVO)2 (O)4(L2)2(py)6] (2) were prepared and characterized. Due to the conformational flexibility of the ligands, both entities exhibit very peculiar metal topologies and composition, differing significantly from structural patterns established in the related chemistry of divalent 3d metals. Structural analysis also unveils the existence of the most complex metallamacrocycles from this family to date. Studies of the magnetic properties via bulk magnetization measurements and EPR spectroscopy confirmed the existence of uncoupled long-distant S = 1/2 metal centers and the spin ground states S = 2 and S = 1 of the clusters

A bis-vanadyl coordination complex as a 2-qubit quantum gate

A new bis-hydroxyphenylpyrazolyl ligand, H4L, allows isolating and structurally characterizing vanadyl and titanyl dinuclear complexes (Bu4N)2[(MO)2(HL)2] (M = V, Ti). The weak dipolar coupling and relatively short quantum coherence of the divanadyl anions are optimal for a 2-qubit molecular architecture proposed to implement electron-mediated nuclear quantum simulations.This research was supported by Spanish MINECO (CTQ2015-68370-P, PGC2018-098630-B-I00, MAT2017-86826-R, CTQ2015-64486-R), the Aragón government (E31_17R) and EU quantERA (SUMO, PCI2018-093106, PCI2018-093116), and used resources of the ALBA synchrotron and of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DEAC02-05CH11231. G. A. thanks the Generalitat de Catalunya for the prize ICREA Academia 2018.Peer reviewe

Novel Topologies in Vanadium-bis-β-Diketone Chemistry: A [V4] and a [V6] Metallacyclophane

Exploring the chemistry of vanadyl ions (VO2+) with bis-ß-diketone ligands, in pyridine reactions of vanadyl sulfate with 1, 3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-benzene (H4L1) and 1, 3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, (VIVO)4(H2L1)4(py)4] (1) and (VVO)4(VIVO)2 (O)4(L2)2(py)6] (2) were prepared and characterized. Due to the conformational flexibility of the ligands, both entities exhibit very peculiar metal topologies and composition, differing significantly from structural patterns established in the related chemistry of divalent 3d metals. Structural analysis also unveils the existence of the most complex metallamacrocycles from this family to date. Studies of the magnetic properties via bulk magnetization measurements and EPR spectroscopy confirmed the existence of uncoupled long-distant S = 1/2 metal centers and the spin ground states S = 2 and S = 1 of the clusters

Photoswitching the cytotoxic properties of Platinum(II) compounds

et al.The photoactivation of potential anticancer metal complexes is a hot topic of current research as it may lead to the development of more selective drugs. Photoactivated chemotherapy (PACT) with coordination compounds is usually based on a (photo)chemical reaction taking place at the metal center. Herein, a new strategy is exploited that consists of “photomodifying” a ligand coordinated to metal ions. Platinum(II) complexes from photoswitchable 1,2-dithienylethene-containing ligands have been prepared, which exhibit two interconvertible photoisomeric forms that present distinct DNA-interacting properties and cytotoxic behaviors.P.G. acknowledges the Institució Catalana de Recerca i Estudis Avançats, the Ministerio de Economía y Competitividad of Spain (Project CTQ2011-27929-C02-01), and COST Action CM1105. This work was partially supported by a grant from the Spanish government, the EU (FEDER) (FIS PI13/00089), La Marató de TV3 Foundation (20132730), and an individual grant from Fundação para a Ciência e Tecnologia of the Portuguese Ministry of Science and Higher Education to L.K.G. (SFRH/BPD/91766/2012).Peer reviewe

Site selective 3d heterometallic molecular strings based on bis-β-diketone ligand

Resumen del trabajo presentado a la: "14th International Conference on Molecule-Based Magnets" celebrada en San Petersburgo (Rusia) del 5 al 9 de julio de 2014.One of the major challenges of coordination chemistry today is the design and synthesis of molecules with predetermined functions and physicochemical properties. Our research group is addressing this challenge through the preparation of polydentate ligands from the bis-β-diketone family, capable of gathering transition metals within molecular clusters of well-defined nuclearity and topology. Known structural motifs arising from these platforms are weakly coupled cluster pairs as prototypes of 2-qubit quantum gates, and chain-like arrays as potential prototypes of molecular wires. One of the ligands capable to accommodate metal ions into linear chains is trispyridyl/ bis-β-diketone, H2L, (1,3-bis-(3-oxo-3-(2-pyridyl)propionyl)pyridine) as demonstrated with the synthesis of the supramolecular array [Co4L2(MeOH)8](NO3)4 and its analogues. We are now presenting the potential of this ligand for the preparation of new 3d heterometallic molecular strings with site selective metal composition as a direct consequence of crystal field energy effects. Among them, the most interesting cases are tetranuclear and octanuclear Co-Ni systems where two very similar metals are easily differentiated due to the above described selectivity. From the synthetic point of view, it will be shown how small changes in reaction conditions can vary the nature of the obtained system leading from charged species to neutral molecules. The solid state and solution behaviour of those systems will be discussed following crystallographic, spectroscopic, magnetic and redox studies.We are grateful to the ERC for a financial support under Starting Grant 258060 FuncMolQIP.Peer reviewe