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The condensation reactions between (4-amino-2,6-dichlorophenyl)bis(2, 4,6-trichlorophenyl)methyl radical and acetylacetone or 1, 4-bis(5-methyl-2-thienyl)-1,4-butanedione yield [2,6-dichloro-4-(2, 5-dimethyl-1-pyrrolyl)phenyl]bis(2,4,6-trichlorophenyl)methyl radical (3(*)()) and [2,6-dichloro-4-[2, 5-bis(5-methyl-2-thienyl)-1-pyrrolyl]phenyl]bis(2,4, 6-trichlorophenyl)methyl radical (4(*)()), respectively. EPR studies of both radicals 3(*)() and 4(*)() in CH(2)Cl(2) solution suggest a weak electron delocalization with coupling constant values of 1.25 and 1.30 G, respectively, with the six aromatic hydrogens. Their electrochemical behavior was analyzed by cyclic voltammetry. Both radicals show reversible reduction processes at E degrees = -0.69 V and -0.61 V versus SSCE, respectively, and anodic peak potentials at E(p)(a) = 1.10 and 0.72 V, respectively, versus SSCE at a scan rate (nu) of 200 mV s(-)(1), being reversible for radical 4(*)(). X-ray analysis of radical 3(*)() shows a high value (65 degrees ) of the dihedral angle between the 2,5-dimethylpyrrolidyl moiety and the phenyl ring. Smooth oxidation of radical 4(*)() in CH(2)Cl(2) containing trifluoroacetic acid gives an ionic diradical species with a weak electron interaction (|D/hc| = 0.0047 cm(-)(1)). A Curie plot of the Deltam(s)() = +/-2 signal intensity versus the inverse of the absolute temperature in the range between 4 and 70 K suggests a triplet or a nearly degenerate singlet-triplet ground state.

The synthesis of 4,4-iminobis(2,2′,2″,4′,4″,6,6′,6″-octachlorotriphenylmethyl) diradical3, a stable organic magnetic molecule consisting of two spin-containing fragments linked by a nitrogen atom, is reported. Electron paramagnetic resonance (EPR) analysis in methyltetrahydrofuran solution (∼10–3 m) at low temperatures showed a typical fine structure (gxx=2.0042;gyy=2.0048;gzz=2.0027) of Δms=±1transition( | D/hc |=0.0071 cm–1; | E/hc |=0.0006 cm–1) as well as a broad (ΔHpp=7.5 G) and weak signal of Δms=±2 transition (g=4.124), due to an asymmetric and excited triplet state corresponding to an intramolecular spin–spin interaction which diminishes with decreasing temperature. It also showed a pair of small peaks, that might be associated with a weaker dipole–dipole interaction which diminishes with increasing temperature, emerging at both sides of a central and single peak due to a doublet state resonance corresponding to 2,2′,2″,4′,4″,6,6′,6″-octachloro-4-{3,5-dichloro-4-[bis(2,4,6-trichlorophenyl)methylene]cyclohexa-2,5-dienylideneamino}triphenylmethyl radical 4, obtained by smooth oxidation of 3. From magnetic susceptibility measurements of the sample in the solid, a linear four-spin model was applied to establish that the singlet is the ground state of the molecule and that two triplets (Jintra=–286±30 K, J′inter=–160±50 K) were the low-lying excited states. Organic solutions of 3 in air slowly oxidize to give 4, a much more persistent monoradical which is also obtained by a smooth oxidation of 3 with AgNO3 in CHCl3 . Cyclic voltammograms for the reduction of 3 and 4 in dimethylformamide (DMF) with tetra-n-butylammonium perchlorate exhibited three consecutive redox couples with standard potentials of –0.23, –0.58 and –0.74 V vs. SCE, indicating a reasonable stability of anions 3–and32– in DMF solution.

(2,6-Dichlorophenyl)bis(2,4,6-trichlorophenyl)methyl radical ( 2 ) has been prepared through a reaction sequence of five stages obtaining four new intermediate compounds 1–4 . Assignment of the structures of these compounds have been completely ascertained by means of their 1 H NMR spectra. The new persistent radical 2 has been characterized by EPR spectra and magnetic susceptibility measurements. The X-ray structural analysis of 2 shows that it adopts a propeller-like conformation with the phenyl rings twisted around their bonds to trivalent carbon. Magnetic susceptibility of 2 is characteristic of a paramagnet with a weak antiferromagnetic interaction at low temperatures (Weiss constant, Θ = −1.8 K).

Tris(2,4,6-trichlorophenyl)carbenium hexachloro-antimonate (2), (2,6-dichloro-4-hydroxyphenyl)bis(2,4,6-trichlorophenyl)methyl radical (4) and its methyl ether derivative 5 have been synthesized and isolated as crystalline solids. In contrast to 5, radical 4 is not very stable in air, and the disappearance of 4 by aerial oxidation has been monitored by UV-vis spectroscopy. The EPR spectra of 4 and 5 are reported and commented upon.

The synthesis, characterization, and physical properties of perchloro-2,6-bis(diphenylmethyl)-pyridine-α,α'-ylene biradical (1) and αH-tricosachloro-2,6-bis(diphenylmethyl)pyridine-α'-yl radical (2) which present exceptionally high stabilities are reported. The synthesis of 1 and 2 have been accomplished using different strategies in order to get them separately, although 1 always contains 2 as an impurity. 1 is a molecule constituted by two trivalent carbon atoms linked by a trichlorom-pyridylene spacer which has proved to be a good ferromagnetic coupling unit. Magnetic susceptibility measurements from 4.2 to 300 K show that the ground state of 1 is the triplet being 2J=358±14 cm -1 (1.03 kcal/mol), the triplet-singlet energy gap. At low temperature, an antiferromagnetic interaction between intermolecular spines was observed (Curie temperature, θ 1 =-2.02±0.10K). The EPR spectrum of 1 in frozen 2-methyltetrahydrofuran (133 K) in the Δm s =±1 region affords three symmetric pairs of lines corresponding to a triplet species without axial symmetry with zfs parameters |D/hc|=0.0081 cm -1 . The Δm s =±2 transition follows the Curie law over the range 10.0-62.o K, supporting the highest multiplicity of the molecule in the ground state. The cyclic voltammogramm of 1 exhibits a redox couple (E°=0.18 V vs SCE) which is attributed to the reduction of this biradical to the stable anion 12 (1 - ), and a second irreversible peak (E p c = -0.25 V vs SCE) which is ascribed to the formation of the unstable dianion 13 (1 2- ). The electronic spectrum of 1 is presented and discussed

Tris(2,4,6-trichlorophenyl)carbenium hexachloro-antimonate (2), (2,6-dichloro-4-hydroxyphenyl)bis(2,4,6-trichlorophenyl)methyl radical (4) and its methyl ether derivative 5 have been synthesized and isolated as crystalline solids. In contrast to 5, radical 4 is not very stable in air, and the disappearance of 4 by aerial oxidation has been monitored by UV-vis spectroscopy. The EPR spectra of 4 and 5 are reported and commented upon.

The synthesis, characterization, and physical properties of perchloro-2,6-bis(diphenylmethyl)-pyridine-α,α'-ylene biradical (1) and αH-tricosachloro-2,6-bis(diphenylmethyl)pyridine-α'-yl radical (2) which present exceptionally high stabilities are reported. The synthesis of 1 and 2 have been accomplished using different strategies in order to get them separately, although 1 always contains 2 as an impurity. 1 is a molecule constituted by two trivalent carbon atoms linked by a trichlorom-pyridylene spacer which has proved to be a good ferromagnetic coupling unit. Magnetic susceptibility measurements from 4.2 to 300 K show that the ground state of 1 is the triplet being 2J=358±14 cm -1 (1.03 kcal/mol), the triplet-singlet energy gap. At low temperature, an antiferromagnetic interaction between intermolecular spines was observed (Curie temperature, θ 1 =-2.02±0.10K). The EPR spectrum of 1 in frozen 2-methyltetrahydrofuran (133 K) in the Δm s =±1 region affords three symmetric pairs of lines corresponding to a triplet species without axial symmetry with zfs parameters |D/hc|=0.0081 cm -1 . The Δm s =±2 transition follows the Curie law over the range 10.0-62.o K, supporting the highest multiplicity of the molecule in the ground state. The cyclic voltammogramm of 1 exhibits a redox couple (E°=0.18 V vs SCE) which is attributed to the reduction of this biradical to the stable anion 12 (1 - ), and a second irreversible peak (E p c = -0.25 V vs SCE) which is ascribed to the formation of the unstable dianion 13 (1 2- ). The electronic spectrum of 1 is presented and discussed

A partially oriented melt-extruded PLA multifilament was false-twist textured to stabilize its structure. Conventional DSC analysis showed a relaxation peak at the end of glass transition. Simultaneous consideration of the TMA curve enabled us to evaluate both the relaxation and the cold crystallisation produced during the DSC scan. The periodic load applied during TMA experiments also enabled us to examine the evolution of Young’s modulus along the glass transition, relaxation and cold crystallisation phenomena. Increases in Young’s modulus and in enthalpy are related because of crystallisation. Texturing increased crystallinity and decreased cold crystallisation of PLA during the DSC scan.