Angel Gutiérrez

Structural, magnetic, electrical and optical characterization of systems built from [M([9]aneN3)2]2+ (M=CuII or NiII) and TCNQ or TCNQF4

Three different supramolecular architectures corresponding to [M([9]aneN 3 ) 2 ](TCNQ) 2 , (M=Ni II 1 or Cu II 2, [9]aneN 3 =1,4,7-triazacyclononane, TCNQ=7,7,8,8-tetracyanoquinodimethane), [Cu([9]aneN 3 ) 2 ](TCNQ) 3 3 and [Cu([9]aneN 3 ) 2 ](TCNQF 4 ) 2 , 4 (TCNQF 4 =2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane), have been prepared and crystallographically characterized: 1, triclinic, P1, a=8.6488(9), b=8.919(3), c=11.316(2) A, α=82.06(2), β=74.331(10), γ=85.71(2)°, Z=1; 2, triclinic, P1, a=8.6806(11), b=8.915(5), c=11.348(2) A, α=82.03(3), β=74.109(14), γ=84.95(2)°, Z=1; 3, triclinic, P1, a=8.350(2), b=9.884(4), c=14.369(4) A, α=74.10(2), β=89.01(2), γ=69.11(2)°, Z=1; 4, triclinic, P1, a=15.476(5), b=16.146(4), c=16.441(4) A, α=77.15(2), β=78.04(3), γ=85.43(3)°, Z=2. Compounds 1 and 2 are formed by dimeric (TCNQ) 2 2– units and 4 by three different dimeric (TCNQF 4 ) 2 2– units. Compound 3 is formed by isolated [Cu([9]aneN 3 ) 2 ] 2+ groups and trimeric (TCNQ) 3 2– units. The electrical, optical and magnetic properties of the four new compounds have been interpreted on the basis of their supramolecular architectures.

Synthesis, crystal structure, spectroscopic study, and magnetic behavior of the first dinuclear Mn(II) complex of hydrazone-based ligand-containing dicyanamide bridging groups

A new dinuclear complex of manganese(II), [Mn(L)(μ1,5-dca)(CH3OH)]2 (1), with dicyanamide anion and (E)-3-hydroxy-N′-(pyridin-2-ylmethylene)-2-naphthohydrazide (HL) was synthesized. The complex was characterized by elemental analyzes, spectroscopic methods, X-ray diffraction, and magnetic susceptibility studies. Two manganese ions in the complex were connected by two bridging dicyanamide ligands in a symmetric end-to-end (μ1,5-dca) fashion. The presence of intramolecular hydrogen bonding in the mononegative naphthohydrazone (L−) affects keto-enol tautomerism and the ligand coordinates to manganese(II) in the keto-form. Magnetic measurements showed an antiferromagnetic interaction between adjacent manganese ions in the dimer.

Combined Influence of Lifestyle Risk Factors on Body Fat in Spanish Adolescents - the AVENA Study

Objective: To examine the combined influence of four lifestyle risk factors related to physical activity, television viewing, sleep duration, and meal frequency on body fat (BF) in adolescents. Method: This cross-sectional study comprised 1,310 Spanish adolescents (age 13–18.5 years). Lifestyle variables were self-reported and BF indicators (weight, height, six skinfold thicknesses, waist circumference) measured during the years 2000–2002. Lifestyle risk factors were: physically inactive, ≧3 h/day watching television, <8 h/day sleep duration, and <5 meals a day. The number of lifestyle risk factors was calculated for each participant, ranging from 0 to 4. Results: The number of lifestyle risk factors was positively associated with sum of six skinfolds, %BF, waist circumference, and waist-height ratio (all p < 0.001). The odds ratios (95% confidence interval) of overweight (including obesity) for groups with 1, 2, and 3–4 lifestyle risk factors compared with those with 0 were 2.86 (1.77–4.62), 3.61 (2.16–6.04), and 5.81 (3.07–10.99), respectively (p for trend <0.001). All the observations were independent of age, gender, race, socioeconomic status, and fat free mass. Conclusion: The combined influence of four lifestyle risk factors is positively associated with BF and an approximately sixfold risk of overweight in adolescents.

Comparing methods of determining addition in presbyopes

Background:  The use of plus lenses to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for near visual tasks. Our aim was to compare the tentative near addition determined using the most common procedures with the final addition prescribed in presbyopic patients.

Five-coordinate nickel(II) xanthate derivatives with triphos. Crystal structure of tris(O-cyclohexyldithiocarbonato)nickelate(II) of bis(2-diphenylphosphinoethyl)phenylphosphine-O-cyclohexyldithiocarbonatonickel(II)

Abstract Five-coordinate complexes, [Ni(S 2 COR)(TRIPHOS)]X (R = cyclo-C 6 H 11 , X = Cl, PF 6 , [Ni(S 2 COC 6 H 11 ) 3 ]; R = Et, X = PF 6 , [Ni(S 2 COEt) 3 ]), have been obtained by the reaction of O-alkyldithiocarbonato complexes, [Ni(S 2 COR) 2 ], with bis(2-diphenylphosphinoethyl)phenylphosphine (TRIPHOS). The structure of [Ni(S 2 COC 6 H 11 ) (TRIPHOS)][Ni(S 2 COC 6 H 11 ) 3 ] was determined by X-ray crystallography. The compound contains a five-coordinate cation and a hexa-coordinate anion. The geometry about the nickel atom in the [Ni(S 2 COC 6 H 11 )(TRIPHOS)] + is distorted trigonal bipyramidal with the axial positions occupied by one sulfur atom of the bidentate O-cyclohexyldithiocarbonate and the central phosphorus atom of the TRIPHOS. In the [Ni(S 2 COC 6 H 11 ) 3 ] − anion, the nickel atom is bonded to six sulfur atoms of three O-cyclohexyldithiocarbonate ligands. Formation of the dithiocarbonato complexes in the reactions of [Ni(S 2 COEt) 2 ] with TRIPHOS has also been observed.

Supramolecular architecture and magnetic properties of copper(II) and nickel(II) porphyrinogen-TCNQ electron-transfer salts.

The compounds [Cu(Tz)-(MeOH)2](TCNQ)2 (1), [Ni(Tz)-(MeOH)2](TCNQ)2 (2), [Cu(Tz)2]-(TCNQ)7 (3) and [Ni(Tz)2](TCNQ)7 (4) (Tz = 2,7,12,17-tetramethyl-1,6,11,16-tetraazaporphyrinogen) were obtained by metathesis reaction of [M(Tz)](ClO4)2 with LiTCNQ and Et3NH(TCNQ)2, respectively. They were characterized by a combination of spectroscopic and physical methods. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 8.310(2), b = 25.180(4), c = 20.727(4) A, beta = 93.58(2) degrees; Z = 4. Compound 3 crystallizes in the triclinic space group P1 with a = 11.244(1), b = 16.700(1), c = 17.321(1) A, a = 113.47(1), beta = 108.52(1), gamma = 96.12(1) degrees; Z = 2. The asymmetric unit of the compound 1 is formed by cationic [Cu(Tz)(MeOH)2]2+ and by two crystallographically non equivalent TCNQ.- anions; these anions form dimeric units by overlap of the pi clouds. The dimers form hydrogen bonds with the metal-lomacrocyclic cation through the methanol ligands. According to this structure the compound is paramagnetic and behaves as an insulator in the temperature range studied. The paramagnetism arises only from the metal-complex moieties. Compound 3 shows an unprecedented structure due to the steric requirements of the macrocycle that favors the stacking of the TCNQ groups. The structure consists of infinite stacks of TCNQ units separated by the metal-macrocyclic units; there are seven TCNQ molecules per formula unit, one of which is formally mono-anionic, while the other six bear one half of an electron per molecule. The copper is six-coordinate in a very distorted octahedral environment. The Tz ligand is located in the equatorial plane and the apical nitrogens of the nitrile groups of two TCNQ molecules complete the coordination around the copper. The compound is a semiconductor and its magnetic behavior can be explained by the sum of the Curie contribution of the metal complex and the contribution arising from the magnetic-exchange interactions of the spins located on the TCNQ units. The latter is found to be typical of one-dimensional antiferromagnetic distorted chains of S = 1/2 spins and can be fitted according to a one-dimensional Heisenberg antiferromagnetic model.

Magnetic and optical characterization of one-dimensional isostructural σ-bonded tetracyanoquinodimethanido complexes of nickel(II) and copper(II)

The complex [CuL(tcnq)2][L = 3,10-bis(2-hydroxyethyl-1,3,5,8,10,12-hexaazacyclotetradecane); tcnq = 7,7,8,8-tetracyanoquinodimethane] has been prepared and crystallographically characterized. Its structure consists of linear chains of alternating copper–macrocycle and tetracyanoquinodimethanide dimers σ bonded to the copper atoms through a nitrile group. The compound is an insulator. The magnetic properties of both the copper and corresponding nickel compounds are the sums of the contributions arising from the transition-metal ion in octahedral symmetry and of (tcnq)22– dimers. The magnetic data were fitted by a model which accounts for contributions from independent Curie spins for the cation and a thermally activated triplet state for the dimerized anions. No magnetic interactions between the metal ion and tcnqs have been observed, even at low temperatures.

Reactivity of ruthenium complexes with uninegative (X,S)-donor ligands (X=S,P). II: Phosphine substitution in [Ru(S,S)2(PR3)2] derivatives, crystal structure of trans-bis(O-ethyldithiocarbonate)bis(dimethylphenylphosphine)-ruthenium(II)

Abstract The complexes [Ru(S,S)2(PPh3)2] [S,S  EtCOCS2−, (CH2)4NCS2−] react with a variety of tertiary phosphines with the substitution of triphenylphosphine and the formation of [Ru(S,S)2(PR3)2]. The reaction occurs with the formation ofthe cis isomer, except for the complex with PMe2Ph that gives rise to the trans isomer as the crystal structure shows. The effect of the different phosphines on the ruthenium complex is analysed in terms of the spectroscopic and electrochemical properties of the isolated compounds. The cyclic voltammetric studies of the cis complexes show that isomerization to the trans isomer occurs on oxidation. This isomerization is not observed in the trans-[Ru(S,S)2(PMe2Ph)2] complexes that give rise to stable trans-ruthenium(II)/ruthenium(III) couples. In a similar way the diphosphine complexes afford a quasi-reversible cis-ruthenium(II)/ruthenium(III) process.

Electrochemical synthesis and studies on the reactivity of heterocylic-thionato derivatives of nickel(II) with nitrogen donor bases

Abstract The [Ni(S,N)2] complexes (S,N = 1,3-thiazolidine-2-thionato, tzdt, 1,3-thiazoline-2-thionato, tzt, and 2-mercaptobenzothiazolato, mbt) have been obtained in good yield by direct electrochemical oxidation of nickel in the presence of the corresponding ligand. The [Ni(tzdt)2] and [Ni(mbt)2] derivatives react with nitrogen donor bases to give the adducts [Ni(S,N)2(L)2] (L = substituted pyridines and primary amines) and [Ni(S,N)2L] (L = bpy, phen, dmp) also obtained by direct electrochemical synthesis. A crystal structure analysis shows that in [Ni(mbt)2(dmp)] the hexacoordinated environment of the nickel atom is formed by two bidentate mbt ligands and one dmp ligand.

N-bonded TCNQ in stacked dimeric systems. Synthesis and crystal structure of [Ru(PPh3)2(TCNQ)]2(TCNQ = 7,7,8,8-tetracyanoquinodimethane)

The reaction of [Ru(CO)2(PPh3)2(thf)2](BF4)2(thf = tetrahydrofuran) with PPh3 in CH2Cl2 and LiTCNQ in methanol leads to the formation of [Ru(PPh3)2(TCNQ)]; the crystal structure of this compound shows a tetrahedral environment of the ruthenium atom with the TCNQ molecule coordinated via N.