C. Rovira

Nonlinear optical properties of polychlorotriphenylmethyl radicals: towards the design of "super-octupolar" molecules

Abstract Molecular quadratic hyperpolarizability ( β c ) of substituted polychlorinated triphenylmethyl radicals, 1 – 8 , has been determined by using the harmonic light scattering (HLS) technique. Results showed that this opens-shell family known to possess a good chemical stability also exhibited a very large SONLO response. The presence of a permanent dipole moment in the ground state for some of these octupolar compounds makes them attractive candidates for further orientation by the poling technique. Data of compounds 1 – 8 have been discussed on the basis of a model describing the evolution of the β c response for D 3h and C 2v symmetry groups.

Organic metals as active components in surface conducting semi-transparent films

Criteria for the selection of molecular metals as the active components of conducting bi-layer composite films are presented and discussed. It is shown that two-dimensional (2D) organic metals with halide or trihalides anions have some advantages over other molecular metals for the conducting bi-layer composite film preparation.

A new (63)(69.81) non-interpenetrated paramagnetic network with helical nanochannels based on a tricarboxylic perchlorotriphenylmethyl radicalElectronic supplementary information (ESI) available: additional crystallographic data. See http://www.rsc.org/suppdata/cc/b3/b315147f/

The reaction of a 3-connecting PTMTC radical and a 2-connecting 4,4′-bipyridine ligands with Co(MeCOO)2·4H2O forms a paramagnetic non-interpenetrated supramolecular network, Co(PTMTC)(4,4′-bpy)(H2O)3·6EtOH·2H2O (MOROF-2), with an unprecedented (63)·(69.81) topology exhibiting helical nanochannels.

Nonlinear optical properties of a new stable ferrocenyl Schiff-base polychlorotriphenylmethyl radical

Here we report the NLO properties of the isomeric trans and cis forms of radical 1. This fact allowed us to prove the feasibility of polychlorotriphenylmethyl radicals as building blocks with electron acceptor ability for NLO materials. Moreover, by comparing the β vec values obtained for isomers trans-1 and cis-1 with those of related ferrocenyl-based chromophores, we propose that molecular torsions strongly decrease the second-order NLO response.

Metal-radical chains based on polychlorotriphenylmethyl radicals: synthesis, structure, and magnetic properties

We report the synthesis, crystal structures, and magnetic properties of two new metal-radical chains built up from a new class of organic radical-based ligands, the polychlorinated triphenylmethyl (PTM) radicals. Crystal structures of two new 1D coordination polymers, [Cu(2)(PTMDC)(2)(py)(5)(EtOH)].3EtOH (1) and [Co(2)(PTMDC)(2)(DMF)(2)(H(2)O)(6)].5DMF (2) (where PTMDC is a PTM radical functionalized with two carboxylic groups), show similar chain-like structures, in which each of the PTMDC radicals are connecting two Cu(II) or Co(II) metal ions. Therefore, from a magnetic point of view, both structures describe a magnetic chain model based on the PTMDC-M(II) unit. In this manuscript, the magnetic exchange coupling constants between both metal ions and the bridging PTM radicals have been determined. In both cases, the temperature dependence of the magnetic susceptibility reveals antiferromagnetic exchange coupling constants between the PTMDC radicals and Cu(II) (J/k(B) = -42 K) and Co(II) (J/k(B) = -14.6 K) ions based on the exchange Hamiltonian H = -J sum S(A(i))S(A(i+1)).

Infrared investigation of the low-temperature structural and magnetic transitions in the spin-ladder candidate(DT−TTF)2Au(mnt)2

We report measurements of the variable temperature infrared response of the organic spin-ladder candidate dithiophentelrathiafulvalene gold maleonitrile dithiolate [(DT-TTF) 2 Au(mnt) 2 ]. The 220 K structural transition isdriven by massive symmetry breaking along the rung direction, whereas the 70 K magnetic transition is associated with a change in symmetry of the vibronically activated A g modes in the rail direction. From molecular dynamics simulations, we assign the most important intramolecular vibrational modes involved in each transition. From an analysis of the charge-transfer behavior, we find that the localization of unpaired electrons in the interacting DT-TTF double chains is modified at these transition temperatures as well. To motivate future inelastic neutron-scattering studies, we have also calculated the spectrum of low-lying magnon excitations expected in this material, assuming an isotropic Heisenberg spin-ladder model. We estimate a gap of 0.6 meV for the one-magnon mode.

Complexation of C60 with the multisulphur π-electron donor BETTTF. spectroscopic characterization and crystal structure of the ternary charge-transfer complexes (C60)(BETTTF)(solvent)

Abstract Two-dimensional close-packed layers of C60 are found in the two isostructural charge-transfer complexes of ternary compositon C60:BET TTF:C7H8 and C60:BET TTF:C7H5Cl. In spite of the close contacts between C60 molecules inside the layers, the crystals are electrical insulators, which is accounted for by the very low degree of charge-transfer between the donor and acceptor molecules revealed in their electronic and EPR spectra.

New dithiothiophene complexes for conducting and magnetic materials

New Ni and Au complexes with 2,3-dihydro-5,6-thiophenedithiolate (dtpdt) 2,3-thiophenedithiolate (a-tpdt), and 3,4-thiophenedithiolate (tpdt) have been prepared and characterised. Their ability to be used as building blocks for novel conducting and magnetic materials is demonstrated by different new compounds, the most remarkable being Au(α-tpdt) 2 , a neutral complex exhibiting metallic properties. Several magnetic materials were obtained as salts with decamethyl metallocene cations. The magnetic field/temperature phase diagram of [Fe(Cp * ) 2 ][Ni(α-tpdt) 2 ] is presented.

A new family of conducting and magnetic charge-transfer salts from BMDT-TTF

Crystals suitable for X-ray structure determination have been obtained from the electrocrystallisation of BMDT-TTF donor, bis(methylenedithio)tetrathiafulvalene, with (N-quinolinium)[Cr(NCS) 4 (quinoline) 2 ], although, due to a ligand exchange during the electrocrystallisation, it has been found that the product is in fact (BMDT-TTF) 4 [Cr(NCS) 6 ]. In this salt the anions and the donors form segregated layers. A salt from BMDT-TTF and (N-isoquinolinium)[Cr(NCS)4(isoquinoline) 2 ] has also been prepared. Raman, EPR and NIR measurements have also been carried out.

Synthesis and study of isomeric multisulfur π-donors BTDM-TTF and BET-TTF and their CT complexes

Abstract A synthetic route that allows to obtain four different multisulfur π-organic donors based on the tetrathiafulvalene structure is given. The synthesized donors which have one sulphur atom in each of the outer rings, are BTDM-TTF [1], trans -BET-TTF [2], and their aromatic counterparts; i.e., DT-TTF [3] and α-T-TTF [2]. Structure of trans -BET-TTF has been confirmed by single crystal X-ray diffraction. Generation and EPR characterizations, both in solution and in the solid state of their cation-radicals are also presented.