Biomedical subjects
Publications and source records attributed to Bruno Donnadieu.
(Amino)(silyl)carbenes, prepared by substitution reactions at a carbene center, can survive several days at 0 degrees C. These species are not push-pull carbenes as their phosphino analogues and therefore are excellent ligands for transition-metal centers.
Two spin-crossover (SCO) complexes [Fe(II)(3-MeO,5-NO2-sal-N(1,4,7,10)] (1) and [Fe(II)(3-EtO,5-NO2-sal-N(1,4,7,10)] (2) have been prepared and studied (3-MeO,5-NO2-sal-N(1,4,7,10) and 3-EtO,5-NO2-sal-N(1,4,7,10) are deprotonated 2-[12-(hydroxy-3-methoxy-5-nitrophenyl)-2,5,8,11-tetraazadodeca-1,11-dien-1-yl]-2-methoxy-4-nitrophenol and 2-[12-(hydroxy-3-ethoxy-5-nitrophenyl)-2,5,8,11-tetraazadodeca-1,11-dien-1-yl]-2-ethoxy-4-nitrophenol, respectively). The X-ray diffraction analysis of complex 1 (C22H26N6O8Fe) evidenced the same Pbnb orthorhombic system at 160 K (high-spin (HS) state) and 100 K (low-spin (LS) state). At 160 K, a = 8.4810(9) A, b = 14.7704(14) A, c = 18.769(2) A, V = 2351.2(4) A3, and Z = 4. At 100 K, a = 8.5317(8) A, b = 14.4674(15) A, c = 18.814(2) A, and V = 2322.2(4) A3. Complex 2 (C28H38N6O9Fe) crystallizes in the P1 triclinic system. At 160 K (HS state), a = 10.265(4) A, b = 10.861(4) A, c = 14.181(5) A, alpha = 84.18(4) degrees, beta = 70.53(5) degrees, gamma = 88.95(5) degrees, V = 1482.6(10) A3, and Z = 2. The iron(II) coordination sphere is distorted octahedral in 1 and 2 with a cis-alpha arrangement of the N4O2 donor set of the hexadentate ligand. The molecules are connected into 1D infinite chains through hydrogen contacts involving the secondary amine functions and O(nitro) atoms of the ligands in adjacent molecules. Investigation of their magnetic properties and Mossbauer spectra has revealed very different SCO behaviors: complex 1 exhibits a cooperative SCO without residual LS or HS fraction; complex 2 shows a LS <--> HS SCO involving approximately 5% of the Fe(II) ions in the 30-150 K range. The phenomenological cooperative interaction parameter J = 138 K evaluated from the area of the hysteresis loop indicates a cooperative effect weaker in 1 than in [Fe(II)(5NO2-sal-N(1,4,7,10))]. The theoretical approach to the SCO in 2 indicates a HS ground state and a LS first excited level 53 K above: the thermal dependence of the system occurs through population of vibrational states. Comparison of the structural and electronic properties of the ferrous SCO materials with parent N4O2 ligands shows that the properties of SCO are closely related to intermolecular interactions and crystal packing.
The monometallic precursors L1Cu and L2Cu (L1H2 standing for 1,3-bis((3-ethoxysalicylidene)amino) propane and L2H2 standing for 1,2-bis((3-methoxysalicylidene)amino) ethane) react with sodium dicyanamide (dca) (NaN3C2), a mixture of gadolinium nitrate, and sodium dicyanamide to yield heterodinuclear L2CuNa(NCNCN) and L1CuGd(NO3)(NCNCN)2 entities. The structural determination shows that two Cu-Na entities are linked by dca with an original mu1,1 coordination mode, evidenced here for the first time, to yield tetranuclear complexes. Two hydrogen bonds operate between the water molecule coordinated to one of the sodium ions and the free nitrogen atoms of two dca ligands, yielding infinite zigzag chains. The structural determination of the Cu-Gd entities indicates that they are held together by two dca ligands, bridging alternately Cu to Gd and Gd to Gd cations, in the more common mu1,5 mode to yield a one-dimensional (1D) network. The dca ligands are not able to transmit interaction between the magnetically active centers in these chains, which are the unique example of structurally characterized Cu-Gd complexes involving dca ligands.
Herein, we report on (31)P(31)P solution-phase "through-space" nuclear spin-spin coupling constants (J(PP)) from a novel family of organometallic tetraphosphine nickel and palladium complexes. These J(PP) constants were accurately determined through NMR iterative simulation based on the second-order spectra obtained for the compounds. The corresponding solid-state X-ray structures of the complexes were determined, and the "through-space" P.P distances are reported. Due to the blocked conformation of the species in solution, a qualitative and semiquantitative experimental correlation is obtained, which links the geometric parameters and the intensity of the corresponding P.P coupling constant. The lone-pair overlap theory developed for (19)F(19)F and (15)N(19)F "through-space" couplings in organic compounds [J. Am. Chem. Soc. 1973, 95, 7747-7752; 2000, 122, 4108-4116] appears to be a reliable foundation on which to account for our results. Based on the reported observations, the lone-pair overlap model is extended to "through-space" (31)P(31)P coupling, and the model is broadened to encompass metal orbital contributions for coordination complexes. Some of the predictions and consequences of the proposed theory are discussed.
[NH(4)](2)Mn(3)(H(2)O)(4)[Mo(CN)(7)](2).4H(2)O (1) has been synthesized by slow diffusion of aqueous solutions containing K(4)[Mo(CN)(7)].2H(2)O, [Mn(H(2)O)(6)](NO(3))(2), and (NH(4))NO(3). Compound 1 crystallizes in the monoclinic C2/c space group. The basic motif of the three-dimensional structure consists of a Mo1-Mn1 gridlike sheet parallel to the bc plane. Two of these sheets are connected through CN-Mn2-NC linkages to form a bilayer reminiscent of the K(2)Mn(3)(H(2)O)(6)[Mo(CN)(7)](2).6H(2)O (2) two-dimensional structure. In 1, [NH(4)](+) cations allow these bilayers to be connected through direct Mo1-CN-Mn1 bridges to form a three-dimensional network, whereas in 2, they are isolated by (H(2)O)K(+) cations. As shown by the magnetic measurements, this increase of dimensionality by counterion substitution induces an enhancement of the ferrimagnetic critical temperature from 39 K in 2 to 53 K in 1.
Two copper(II)-gadolinium(III) metal complexes of formula CuIIGdIIILX3 are reported. H2L stands for the Schiff base ligand obtained by condensation of 3,4-dimethoxysalicylaldehyde with ethylenediamine (complex 1) or 1R,2R-(+)-1,2-diphenylethylenediamine (complex 2). While 1 reveals a centrosymmetric crystal structure, 2 crystallizes in the noncentrosymmetric P212121 space group and exhibits an efficiency 0.3 time that of urea in second harmonic generation. Due to a trend for dissociation in solution, the molecular hyperpolarizabilities (beta) cannot be determined experimentally for 1 and 2. Nevertheless, the electric field induced second harmonic (EFISH) technique, in connection with spectroscopic data and a ZINDO semiempirical approach, leads to a beta value of -6.5 x 10(-30) cm5 esu(-1), for the related CuIIL monomers, as an indicative range of magnitude in all these Schiff base complexes. In addition, 1 and 2 exhibit a ferromagnetic coupling in solid state with J = 3.3 and 1.3 cm-1, respectively (J being the parameter of the exchange Hamiltonian = -JSCu x SGd).
Stable tert-butyl diisopropylamino carbene is more nucleophilic but also more electrophilic than diamino carbenes; it undergoes cyclopropanation reactions and easily binds to metal fragments.
Explore the source record for details and available documents.
The manganese(III) complexes studied in this report derive from asymmetrical trianionic ligands abbreviated H(3)L(i) (i = 4-6). These ligands are obtained through reaction of salicylaldehyde with "half-units", the latter resulting from monocondensation of different diamines with phenylsalicylate,. Upon deprotonation, L(i) (i = 4-6) possess an inner N(2)O(2) coordination site with one amido, one imine, and two phenoxo functions, and an outer amido oxygen donor. The trianionic character of such ligands yields original neutral complexes with the L/Mn stoichiometry. The crystal and molecular structures of three complexes have been determined at 190 K (1) or 180 K (2 and 3). Complex 1 crystallizes in the triclinic space group P (No. 2): a = 7.8582(14) A, b = 10.9225(16) A, c = 12.4882(18) A, alpha = 67.231(14) degrees, beta = 72.134(14) degrees, gamma = 82.589(13) degrees, V = 940.6(3) A(3), Z = 2. Complex 2 crystallizes in the orthorhombic space group Pbcn (Nuomicron. 60): a = 23.8283(15) A, b = 11.1605(7) A, c = 26.152(2) A, V = 6954.8(8) A(3), Z = 8, while complex 3 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 11.7443(14) A, b = 7.5996(10) A, c = 18.029(2) A, beta = 100.604(10) degrees, V = 1581.6(3) A(3), Z = 4. Owing to hydrogen bonds and pi-pi stackings, the mononuclear neutral molecules of 1 are arranged in a 2D network while complexes 2 and 3 are tetranuclear and polymeric (1D chain) species, respectively, owing to the bridging ability of the oxygen atom of the amido function. The experimental magnetic susceptibilities of complexes 2 and 3 indicate the occurrence of similarly weak Mn(III)-Mn(III) antiferromagnetic interactions (J = -1.1 cm(-1)). Single ion zero-field splitting of manganese(III) must be taken into account for satisfactorily fitting the data by exact calculation of the energy levels associated to the spin Hamiltonian through diagonalization of the full matrix for axial symmetry in 2 (J = - 1.1 cm(-1), D(1) = 2.2 cm(-1), D(2) = -2.8 cm(-1)), D(1) and D(2) being associated to the six- and five-coordinate Mn ions, respectively. A weaker antiferromagnetic interaction (J = - 0.2 cm(-1)) operates through pi-pi stacking in complex 1. Complex 3 is a weak ferromagnet (ordering temperature approximately 7 K) as a result of the spin canting originating from the crystal packing.
[(C(5)H(5))Fe(C(5)H(4)COCH=CHC(6)H(4)NEt(2))] (1) has been electrochemically evaluated toward different cations in solution. Calcium sensing by this compound and its two new derivatives [(C(5)H(5))Fe(C(5)H(4)CO(CH=CH)(2)C(6)H(4)NMe(2))] (2) and [(C(5)H(5))Fe(C(5)H(4)CH=CHCOCH=CHC(6)H(4)NEt(2))] (3) that exhibit a conjugated link between the ferrocene unit and the nitrogen atom has been thoroughly examined. Compounds 2 and 3 have been structurally characterized by single-crystal X-ray diffraction studies. The three related protonated species [1H][BF(4)] (4), [2H][BF(4)] (5), and [3H][BF(4)] (6) have been isolated in a good yield. NMR experiments clearly established that calcium interaction occurs in the vicinity of the carbonyl group, and mass spectrometry studies confirmed that this interaction, which involves several ligand-Ca(2+) adducts, is complex. A combination of electrochemical and NMR experiments highlighted an original salt influence on the electrochemical calcium sensing result.
The novel dimer [Cp(2)Zr[upper bond start]([minus sign in circle])S([plus sign in circle])CH(Ph)CH[double bond]C[upper bond end]PPh(2)](2), the first example of a structurally characterised sulfur-bridged binuclear zirconathiolane complex, was prepared, characterised by NMR spectroscopy and X-ray crystallography, and some aspects of its solution behaviour were studied.
The crystal structure of 3,7,11,18,22,26-hexaazatricyclo[26.2.2.2(13,16)]tetratriaconta-1(31),13(34),14,16(33),28(32),29-hexaene hexahydrobromide salt [(H6P3)Br6] has been determined by means of X-ray diffraction analysis. It crystallizes with an additional molecule of ethanol and half a molecule of water per molecule of the hydrobromide P3 ligand. The protonation constants of P3 and its host-guest interactions with monophospate (Ph) and pyrophosphate (Pp) have been investigated by potentiometric equilibrium methods. Ternary complexes are formed in aqueous solution as a result of hydrogen bond formation and Coulombic interactions between the host and the guest; formation constants for all the species obtained are reported and compared with the isomeric 3,7,11,19,23,27-hexaazatricyclo[27.3.1.1(13,17)]tetratriaconta-1(33),13, 15,17(34),29,31-hexaene (Bn) ligand. For the H6P3Pp(2+) those bonding interactions reach a maximum yielding a log KR6 of 5.87. The selectivity of the P3 ligand with regard to the monophosphate and pyrophosphate substrates (S) is discussed and illustrated with global species distribution diagrams showing a strong preference for the latter over the former as a consequence of the much stronger formation constants with pyrophosphate. An analysis of the isomeric effect is also carried out by comparing the P3-S versus Bn-S systems. In the best case, a selectivity of over 88% is achieved for the diphosphate complexation when using the meta isomer over the para, due solely to the size and shape of the receptors cavity.
The reaction between VO(OR)(3) (R = (i)()Pr, (t)()Bu, CH(2)CF(3)) and the chelating dianionic bis(phenoxy)amine ligand [ONNO]H(2) affords a mixture of two isomers (A and B in a ratio A:B approximately 3:1) formulated as VO(OR)[ONNO] (1a-c) (R = (i)()Pr (1a), (t)Bu (1b), CH(2)CF(3) (1c)). Multinuclear and NOESY NMR spectroscopy experiments were able to determine the structure in solution of the complexes. Both isomers have the symmetry-related phenolate groups in a trans configuration, the difference arising from the different configuration of the oxo and alkoxo ligands being located either cis (in isomer A) or trans (in isomer B) to the tripodal amino nitrogen donor atom and the (dimethylamino)ethyl sidearm respectively for the oxo and the alkoxo ligands. Crystals of isomer A (cis-1a) were obtained, and the structure determination confirms the arrangement of the ligands around the vanadium center. Analogue complexes VO(X)[ONNO] (X = Cl (2); X = N(3) (3)) were prepared by reacting equimolar amount of [ONNO]H(2) and VO(X)(n)(OR)(3-n) (X = Cl, R = Et, n = 1; X = N(3), R = (i)Pr, n = 2) at ambient temperature. Compounds 2 and 3 were further characterized by NMR spectroscopy experiments and X-ray structure determination. For both 2 and 3, a single isomer is obtained, having a trans-(O,O) configuration for the phenolate groups and a trans configuration of the oxo ligand in respect to the tripodal amino nitrogen donor atom. Finally, complex 2 could also be obtained by chlorination of 1a or 3 using a large excess of ClSiMe(3) in refluxing toluene.
A novel heterospin system, [(CuL)Gd(H2O)3(Fe(CN)6)] x 4H2O, is obtained by reacting the mononuclear complex, [CuL], with gadolinium(III) nitrate, followed by the substitution of the nitrato groups with [Fe(CN)6](3-) ions (L2- = N,N'-propylenedi(3-methoxysalicylideneiminato)).
The title compound, namely octaaquaytterbium(III) aquanonachlorotricadmate(II) hexahydrate, [Yb(H(2)O)(8)][Cd(3)Cl(9)(H(2)O)].6H(2)O, was prepared by evaporation at 278 K from an aqueous solution of the ternary system YbCl(3)-CdCl(2)-H(2)O and was characterized by elemental chemical analysis and by X-ray powder and single-crystal diffraction studies. The crystal structure can be viewed as being built from layers of double chains of CdCl(6) and CdCl(5)(H(2)O) octahedra separated by antiprismatic [Yb(H(2)O)(8)](3+) cations. The stabilization of the structure is ensured by O-H.O and O-H.Cl hydrogen bonds. A comparison with the structures of SrCd(2)Cl(6).8H(2)O and CeCd(4)Cl(11).13H(2)O is presented.
The step-by-step synthesis of the first oligophosphazenes having more than two types of side functions is described. These multifunctionalized oligophosphazenes possess up to four phosphazene linkages and up to four types of functional side groups. These compounds may serve as models for a better understanding of electronic delocalization phenomena in linear inorganic chains, and constitute novel cores for the synthesis of new dendrimeric species possessing several types of functions as end groups, at the level of the core, and within the branches.
Explore the source record for details and available documents.
A new tripod N(3) ligand (L), containing three imidazole rings, was synthesized in good yield. At variance with usual aromatic ligands with N(2) or N(3) donor sets such as pyridine or pyrazole derivatives, L stabilizes the Fe(III) oxidation state. The corresponding iron(III) complexes [Fe(L)Cl(3)] (1) and [Fe(L)(2)](ClO(4))(3) (2) were prepared and characterized by X-ray structural analysis and spectroscopic methods. The coordination environment around all the Fe(III) centers has a distorted octahedral geometry. [Fe(L)Cl(3)] (1) belongs to the monoclinic system, space group P2(1)/n, a = 9.7406(5) A, b = 17.207(2) A, c = 14.615(2) A, beta = 104.448(9)(o) Z = 4, V = 2372.1(4) A(3); R = 0.044, R(w) = 0.055. [Fe(L)(2)](ClO(4))(3) (2) belongs to the monoclinic system, space group P2(1)/c, a = 16.1057(15) A, b = 11.1079(12) A, c = 26.283(2) A, beta = 102.062(10)(o), Z = 4, V = 4598.2(8) A(3); R = 0.0465, R(w) = 0.0902. The Fe-N((i)PrIm) bond lengths are systematically longer than the Fe-N(MeIm) ones. Compound 2 is a highly anisotropic low-spin Fe(III) complex displaying a rather unusual EPR spectrum with a sharp signal at g = 3.5 and a broad one at g approximately 1.6. The fitting of this EPR spectrum is discussed.