Mauricio Fuentealba

Synthesis, spectral, structural, second-order nonlinear optical properties and theoretical studies on new organometallic donor-acceptor substituted nickel(II) and copper(II) unsymmetrical Schiff-base complexes.

The synthesis, spectroscopic and structural characterization, linear and nonlinear optical properties, as well as the electrochemical behavior of a series of robust neutral binuclear M[Fc-C(O)CH=C(CH(3))N-X-N=CH-(2-O,5-R-C(6)H(3))] (M = Ni (4), Cu (5), X = o-C(6)H(4), R = H; M = Ni (9), X = CH(2)CH(2), R = OH), and their corresponding ionic trinuclear [M{Fc-C(O)CH=C(CH(3))N-X-N=CH-(eta(6)-2-O,5-R-C(6)H(3))RuCp*}][PF(6)] (6, 7, 10), M[ONNO]-type unsymmetrical Salophen and salen complexes featuring ferrocenyl (Fc) donor and the mixed sandwich acceptor [Cp*Ru(eta(6)- salicylidene)](+) as a push-pull moiety are reported in this paper (Fc = CpFe(eta(5)-C(5)H(4)); Cp = eta(5)-C(5)H(5); Cp* = eta(5)-C(5)Me(5)). The single-crystal X-ray structure of the bimetallic iron-nickel derivative 4 indicates a bowed structure of the unsymmetrical Schiff base skeleton. The Ni(II) ion is tetracoordinated in a square planar environment, with two nitrogen atoms and two oxygen atoms as donors. The new metalloligand [Fc-C(O)CH=C(CH(3))N(H)CH(2)CH(2)N=CH-(2,5-(OH)(2)C(6)H(3))] (8) obtained from the Schiff base condensation of 2,5-dihydroxobenzaldehyde with the half-unit precursor, Fc-C(O)CH=C(CH(3))N(H)CH(2)CH(2)NH(2) (2), is reported with its crystal structure showing partial delocalization of the heteroconjugated [O-C-C-C-N] frameworks with a dihedral angle between the respective planes of 60.76 degrees. Second order nonlinear optical (NLO) measurements were achieved using the Harmonic Light Scattering technique to probe the role of the M[ONNO] chromophores and of the pi-complexation of the salicylidene ring in the nonlinearity. All the complexes exhibit a second-order nonlinear response increasing with the nuclearity, the hyperpolarizability (beta) value of the trinuclear complex 10 being 1.5 time larger than that of the metalloligand 8 (beta = 155 x 10(-30) esu). A rationalization of the structural, electronic, and redox properties of the title compounds is provided, based on a theoretical investigation at the density functional theory (DFT) level. Their UV-visible spectra has been assigned with the help of time-dependent (TD) DFT calculations. They are dominated by LMCT, MLCT, and pi-pi* transitions.

Trinuclear π-conjugated chromophores formed by a neutral ferrocenyl group and a cationic mixed ruthenium sandwich linked through an unsymmetrical Schiff-base complex spacer

The synthesis of neutral dinuclear unsymmetrical Schiff base complexes 1 and 2 was carried out in an one-pot two-step reaction sequence that involves the reaction of 1-ferrocenyl-1,3-butanedione with an excess of ethylenediamine in refluxing CH2Cl2, to generate the intermediate “half-unit” Fc–C(O)CH2C(CH3)NCH2CH2NH2, Fc = (η5-Cp)Fe(η5-C5H4), Cp = C5H5), followed by its in situ templated reaction with salicylaldehyde and nickel(II) or copper(II) acetate in refluxing CH2Cl2–EtOH (3 : 1) mixture. On the other hand, ionic trinuclear unsymmetrical complexes [3]+PF6− and [4]+PF6− were synthesized by reacting dinuclear precursors 1 and 2, respectively, with [(η5-Cp*)Ru(CH3CN)3]+PF6−, Cp* = C5Me5, in refluxing CH2Cl2. Both complexes contain the neutral electron-releasing ferrocenyl group and the cationic electron-withdrawal sandwich, [(η5-Cp*)Ru(η6-arene)]+, connected by a tetradentate {M(ONNO)} chelate (M = Ni, Cu). The new unsymmetrical organometallic Schiff base compounds were characterized by elemental analysis, IR, UV-Vis, 1H NMR and EPR spectroscopy. In addition, the Ni(II) containing complexes 1 and [3]+PF6− were authenticated by X-ray diffraction analysis. Solvatochromic and electrochemical properties were also studied. The organometallic–inorganic hybrid unsymmetrical Schiff base complexes [3]+PF6− and [4]+PF6− can be defined as type I non-rod-shaped dipolar chromophores.

Preparation, characterization and electrochemical and X-ray structural studies of new conjugated 1,1′-ferrocenediyl-ended [CpFe-arylhydrazone]+ salts

A series of new conjugated bimetallic ferrocenyl 1,1′-bis-substituted compounds of the type (E)-[CpFe(η6-p-RC6H4)NHNCH(η5-C5H4)Fe(η5-C5H4)–CHCHC6H4-p-R′]+PF6− (Cp = η5-C5H5; R, R′ = H, NO2, 11; Me, NO2, 12; MeO, NO2, 13; Cl, NO2, 14; Me, CN, 15; Me, Me, 16), with end-capped (E)-ethenylaryl and [CpFe(arylhydrazone)]+ substituents, have been prepared by the condensation reaction of 1,1′-(p-R′-arylethenyl)ferrocenecarboxaldehyde (R′ = Me, 4; NO2, 5; CN, 6) with the organometallic hydrazine precursors [CpFe(η6-p-RC6H4NHNH2)]+PF6− (R = H, 7; Me, 8; MeO, 9; Cl, 10). In the trimetallic series, {[CpFe(η6-p-RC6H4)NHNCH(η5-C5H4)]2Fe}2+[PF6−]2 (R = H, 17; Me, 18; MeO, 19, Cl, 20), which results from the condensation of two equivalents of the same organometallic hydrazine precursor (7–10) with 1,1′-ferrocenedicarboxaldehyde, the ferrocenediyl core symmetrically links two cationic mixed-sandwich units. These ten hydrazones (11–20) were stereoselectively obtained as their trans isomers about the NC double bond. All the new compounds were thoroughly characterized by a combination of elemental analysis, spectroscopic techniques (1H NMR, IR and UV-Vis) and electrochemical studies in order to prove electronic interaction between the donating and accepting units through the π-conjugated system. A representative example of each series has also been characterized by single crystal X-ray diffraction analysis. The bimetallic complex 16+ adopts an anti conformation with the two iron atoms on opposite faces of the dinucleating hydrazonato ligand, whereas the trinuclear complex 192+ adopts a syn conformation with an Fe–Fe–Fe angle of 180°. Other salient features of these structures are the long Fe–Cipso bond distances and the slight cyclohexadienyl character at the coordinated C6 ring, with a folding angle of 7.4° and 7.0° for 16+ and 192+, respectively.

Theoretical and electrochemical studies on organometallic symmetrical Schiff base complexes of Zn(II), Cu(II), Ni(II) and Co(II)

The electronic communication between two redox centres through a Schiff base complex has been investigated in a series of ethylenediimine-bis(1-ferrocenyl-1,3-butanedionate) complexes of Zn(II) 1, Cu(II) 2, Ni(II) 3 and Co(II) 4. Cyclic voltammetry experiments of 1 and 2 exhibit a unique two-electron reversible oxidation wave, whereas in the case of 3 and 4 two and three one-electron oxidation processes are, respectively, observed. These results suggest some electronic interaction between the iron atoms of the ferrocenyl groups. DFT calculations carried out on model complexes show that for all the studied compounds the removal of the first two electrons corresponds to the oxidation processes of the iron centres in the weakly coupled ferrocenyl termini. The electronic communication between the two iron centres increases on going from 1 to 4. Finally, a re-indexation of the bands observed in the UV-Visible spectra has been carried out using TDDFT calculations.

ORGANOMETALLIC 1,5-BENZODIAZEPINE AND 1,5-BENZODIAZE PINIUM COMPOUNDS: SYNTHESIS, CHARACTERIZATION, X-RAY DIFFRACTION STRUCTURES AND THEORETICAL INVESTIGATION

ABSTRACT The organometallic tridentate ketoamine or enaminone compound, (η 5 -Cp)Fe(η 5 -C 5 H 4 )-C(=O)-CH=C(Me)-NH-C 6 H 4 -o-NH 2 , undergoes an intramolecular cyclocondensation promoted by Cu(ClO 4 ) 2 ⋅6H 2 O (2:1 molar ratio) affording the neutral 2-ferrocenyl-4-methyl-1,5-benzodiazepine, 1. However, when the molar ratio used is 1:1, the ketoamine or enaminone compound transforms into the 2-ferrocenyl-4-methyl-1,5-benzodiazepinium cation, [2] + . The X-ray molecular structure of 1 exhibits a seven-membered ring with a boat conformation, and two folding dihedral angles along the N(1)-N(2) and C(11)-C(13) axes. In the case of [2] + , the structure shows only one folding dihedral angle along the N(1)-N(2) axis. A rationalization of the properties of 1 and [2] + is provided through DFT calculations.Keywords: Organometallic diazepine, organometallic diazepinium, DFT calculations, X-ray structures, ferrocenyl ketoamine, ferrocenyl enaminone. INTRODUCTION It is well known in the literature that reactions of β-diketones with 1,2-diamines generally yield symmetrical 2:1 tetradentate Schiff bases whatever their proportion.

X-RAY CRYSTAL AND MOLECULAR STRUCTURE OF AN ORGANOMETALLIC HYDRAZONE CONTAINING A ZIGZAG p-CONJUGATED SPACER: [CpFe(h6-C6H5)-N(Me)N=CH-C 6H4-4-NMe2]+ PF6-

The crystal and molecular structure of the complex [CpFe(h6-C6H5)-N(Me) N=CH-C6H4-4-NMe2] +PF6-, [1]+PF6-, was solved by single crystal X-ray diffraction analysis. One of the most salient features observed in this structure is the depyramidalization of both the benzylic nitrogen and the dimethylamino nitrogen atoms which reveals the delocalization of the p-electron system along the entire hydrazone skeleton from the donor to the acceptor termini, through a quinonoidal deformation and a pseudo-cyclohexadienyl conformation (folding dihedral angle of ca. 7.4°) of the free and coordinated phenyl rings, respectively. Both Cipso-N bond lengths are virtually identical (1.37 A), lying between pure single and double bonds. These and other peculiarities are described and compared with the structures of other organometallic hydrazones

(E)-1-(3-Bromo­phen­yl)-3-(3,4-dimeth­oxy­phen­yl)prop-2-en-1-one

The molecular structure of the title compound, C17H15BrO3, consists of a bromophenyl and a 3,4-dimethoxyphenyl group linked through a prop-2-en-1-one spacer. The C=C double bond displays an E conformation, while the carbonyl group shows an S-cis conformation relative to the double bond.

trans-Bis[1,2-bis­(diphenyl­phosphan­yl)ethane]­chlorido(ethyn­yl)ruthenium(II)

The molecular structure of the title compound, trans-[Cu(C2H)Cl(C26H24P2)2], consists of an RuII cation, located on an inversion centre, in an octahedral environment defined by two chelating phosphines, one acetylide and one chloride ligand. The –C CH and the chlorine ligands are disordered over two equivalent positions (0.5 occupancy each). The coordination geometry is distorted octahedral, with the –C CH fragment and the Cl ligand in trans positions. The four P atoms occupy the equatorial plane of the octahedron and the chloride and acetylide ligands the axial positions.

A NEW LINDQVIST-TYPE HEXAMOLYBDATE CLUSTER FUNCTIONALIZED WITH THE jt-DONOR LIGAND 4-BROMO-2,6-DIMETHYLPHENYLIMIDO: SPECTROSCOPIC, ELECTROCHEMICAL AND STRUCTURAL STUDIES

ABSTRACT A new ionic organic-inorganic hybrid complex of formula (n-Bu 4 N) 2 [Mo 6 O 18 (NR)]⋅½Me 2 CO, R = -C 6 H 2 -2,6-Me 2 -4-Br, (n-Bu 4 N) 2 [1]⋅½Me 2 CO, has been prepared in acetonitrile by reacting tetrabutylammonium α-octamolybdate, (n-Bu 4 N) 4 [α-Mo 8 O 26 ], with 2,6-dimethyl-4-bromoaniline hydrochloride, 2,6-Me 2 -4-Br-C 6 H 2 NH 2 ⋅HCl, using N,N’-dicyclohexylcarbodiimide, (C 6 H 11 )N=C=N(C 6 H 11 ), as dehydrating agent. This complex, formulated as (n-Bu 4 N) 2 [1]⋅½Me 2 CO, contains a C-Br group which can be functionalized for constructing novel hybrid materials. The complex was fully characterized by IR, UV-Vis, 1 H- and 13 C-NMR spectroscopies, and authenticated by single crystal X-ray diffraction analysis. The asymmetric unit contains two crystallographically independent anions, [1] 2- , differing by the orientation of the phenyl ring relative to the hexamolybdate skeleton, and one molecule of acetone. Both molecules differ in the angles Mo(1)-N(1)-C(1)= 172.2(6) and Mo(7)-N(2)-C(9)= 175.6(6)°. These angles, near to 180°, indicate the presence of a Mo≡N triple bond.Keywords: areneimido-derivative, phenylimido-derivative, Lindqvist-type hexamolybdate, polyoxometalate, crystal structure, conformational isomers.

Highly emissive host-guest based on nanoclay intercalated with an Eu3+ complex bearing a new Ru2+ organometallic ligand.

This work describes the design, synthesis and physicochemical properties of the highly emissive nanocomposite [bentonite][Eu{(η5-Cp*)Ru(η6-bzac)}3Phen]0.09[H2O]0.22 based on the Eu(III) complex [Eu{(η5-Cp*)Ru(η6-bzac)}3Phen][PF6]3, bearing a new Ru(II) organometallic β-diketone ligand [(η5-Cp*)Ru(η6-Hbzac)][PF6], intercalated into bentonite-Na+ nanoclay. Single crystal X-ray diffraction analysis of the ligand showed that the [(η5-Cp*)Ru]+ is bound to the phenyl group of a highly planar and conjugated organic β-diketone 1-phenyl-1,3-butanedione (Hbzac) through η6-coordination. The complex was inserted into bentonite-Na+ by ion exchange reactions at room temperature. The products display interlaminar distances and stoichiometries in agreement with the ion exchange capacity and the interlayer space available in the clay. Thermal gravimetric analysis was used to establish the decomposition temperatures of the complex and the nanocomposite, which exceed or border 280 °C. Both compounds exhibit luminescence of high colorimetric purity in the red region. The intensity of the characteristic narrow emission band of Eu3+ in the red region, corresponding to 5D0 → 7F2 transition, is accentuated in the intercalated nanocomposite, reaching a symmetry parameter R = I(5D0 → 7F2)/I(5D0 → 7F1) and Judd–Ofelt Ω2 parameter approximately three and two times larger respectively than that of the starting complex. The ruthenium(II)–europium(III) based nanocomposite is presented as a potential luminescent material with considerably high stability over time.