Juan J. Novoa

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The mechanism of the phase transition of 1-phenyl-3-trifluoromethyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1), the first reported triazinyl radical to present such a feature, is unveiled. In so doing, we identify the key ingredients that are crucial to enable the phase transition in this family of radicals, and how those can be exploited by a rational(More)
The distribution of di-, tri-, and tetracoordination among the d(10) ions of the group 11 metals is theoretically analyzed by means of density functional calculations on more than 150 model complexes of general formula [MX(m)L(n)](1-m) (where M = Cu, Ag, or Au; L = NH(3) or PH(3); X = Cl, Br, or I; m + n = 2-4). The energy of a ligand association reaction(More)
Cu(PPh3)3(TCNE) (TCNE = tetracyanoethylene) and 14 other examples form [TCNE]22- dimers possessing a long 2.89 +/- 0.05 A two-electron four-center (2e-/4c) C-C bond in the solid state. This bond arises from the overlap of the b2g pi* singly occupied molecular orbital (SOMO) on each [TCNE]*- fragment, forming a filled bonding orbital of b2u symmetry, and the(More)
The reaction of Cr(C(6)H(6))(2) and 1,2,4,5-tetracyanopyrazine (TCNP) forms [Cr(C(6)H(6))(2)][TCNP], and TCNP is reduced and forms the eclipsed pi-[TCNP](2)(2-) dimer. Diamagnetic [TCNP](2)(2-) has an intradimer separation of 3.14(2) A. The intradimer C...C and N...N separations are 3.29(2) and 3.42(2) A, respectively, and increase with the distance from(More)
New ferrocenyl Schiff-base polychlorotriphenylmethyl radicals have been synthesized and characterized. The imino group of one such radical undergoes an irreversible trans to cis structural isomerization induced by light. Such photoinduced isomerization has been monitored by UV/Vis and ESR spectroscopy and also monitored by HPLC. ESR frozen solution(More)
Radical anions 1(-•)-5(-•), showing different lengths and incorporating up to five p-phenylenevinylene (PPV) bridges between two polychlorinated triphenylmethyl units, have been prepared by chemical or electrochemical reductions from the corresponding diradicals 1-5 which were prepared using Wittig-Horner-type chemistry. Such radical anions enabled us to(More)
The neutral radical 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA) is a prototype of molecule-based bistable materials. TTTA crystals undergo a first-order phase transition between their low-temperature diamagnetic and high-temperature paramagnetic phases, with a large hysteresis loop that encompasses room temperature. Here, based on ab initio molecular(More)
The magnetic bistability present in some molecule-based magnets is investigated theoretically at the microscopic level using the purely organic system TTTA (1,3,5-trithia-2,4,6-triazapentalenyl). The TTTA crystal is selected for being one of the best-studied molecule-based systems presenting magnetic bistability. The magnetic properties of the high- and(More)
The crystal structure of the spin-canted antiferromagnet beta-p-NCC(6)F(4)CNSSN* at 12 K (reported in this work) was found to adopt the same orthorhombic space group as that previously determined at 160 K. The change in the magnetic properties of these two crystal structures has been rigorously studied by applying a first-principles bottom-up procedure(More)