Observation of a very large internal hyperfine field (62.4 T) in the ferromagnetically ordered state of the S = 1 alpha-iron(II) octaethyltetraazaporphyrin.

The origins of the extraordinarily large internal hyperfine field (62.4 T) for the three-dimensional (weak) ferromagnetically ordered ground state of alpha-Fe(OETAP) are discussed semiquantitatively in terms of existing physical theory. In particular, the classical Fermi-contact contribution to the internal field is found to be highly enhanced by a very large orbital contribution and a significant dipolar term of the same sign. A rationale for the unexpected ordering of this S = 1 non-Kramers system is also presented.

Synthesis, structure, and magnetic characterization of a hysteretic charge-transfer salt metamagnet, decamethylferrocenium 2,3-dicyano-1,4-naphthoquinonide, [Fe(Cp*)2][DCNQ].

The synthesis and single-crystal structure of a new one-to-one charge-transfer salt, derived from decamethylferrocene and 2,3-dicyano-1,4-naphthoquinone, are described. [Fe(Cp*)2][DCNQ] crystallizes in the orthorhombic space group Pbca, with a = 17.3149(5) A, b = 14.6862(4) A, c = 21.0507(6) A, and Z = 8. Magnetization vs temperature data obtained in 100 G suggest that the compound exhibits dominant one-dimensional ferromagnetic coupling and that it subsequently undergoes an antiferromagnetic phase transition below TN approximately 4 K. Results of magnetization vs applied field experiments show that the compound is a metamagnet with a critical field of approximately 3 kG at 1.8 K. In the nominally antiferromagnetic state, apparent canting of the moments gives rise to a small amount of hysteresis. This picture is supported by ac susceptibility data. The 57Fe Mössbauer spectrum exhibits the expected decamethylferrocenium unresolved quadrupole doublet (delta = 0.53 mm/s) at 77 K and magnetic hyperfine splitting, Hint = 37.9 T, corresponding to long-range magnetic order at 1.63 K.

Risk of intracranial hemorrhage and other adverse outcomes after cocaine exposure in a cohort of 323 very low birth weight infants.

We conducted a prospective cohort study of 323 consecutively born very low birth weight infants (< or = 1499 gm) to determine any association between prenatal cocaine exposure and (1) intracranial ultrasonographic abnormalities and (2) other adverse perinatal outcomes. The infants were assigned to either a cocaine-exposed group (n = 86) or a cocaine-nonexposed group (n = 146) on the basis of combined detection methods for prenatal maternal cocaine abuse including maternal history, maternal and infant urine immunoassay (Emit), and meconium analysis (high-performance liquid chromatography and gas chromatography-mass spectrometry). Ninety-one infants were not assigned because of early death before complete testing (n = 80) or missed tests (n = 11). The detected incidence of cocaine exposure in the assigned population was 37% (86/232). Meconium testing with high-performance liquid chromatography and gas chromatography-mass spectrometry was the sole means of detection in 30% (26/86) of cases. The cocaine-nonexposed infants did not differ from the cocaine-exposed infants in the incidence of intraventricular hemorrhage (36% vs 35%), grades III and IV intraventricular hemorrhage (14% vs 14%), or periventricular leukomalacia (4% vs 2%). Adverse outcomes increased by cocaine exposure were abruptio placentae (8% vs 18%; p = 0.046), surgical ligation of a patent ductus arteriosus (1% vs 7%; p = 0.02), and seizures (5% vs 17%; p = 0.004). We conclude that prenatal cocaine exposure does not increase the incidence or severity of intracranial hemorrhage or periventricular leukomalacia but does increase the risk of abruptio placentae, surgical ligation of a patent ductus arteriosus and seizures in very low birth weight infants.

Analysis of meconium for cocaine in neonates.

A solid-phase extraction method was developed for the extraction of first-day meconium samples from premature infants of cocaine-dependent mothers. Extracts were analysed by high-performance liquid chromatography and gas chromatography-mass spectrometry for cocaine and its metabolites. Control stools showed no drug. Meconium from cocaine-dependent mothers showed cocaine in the range 0.1-0.78 micrograms/g. Benzoylecgonine, ecgonine and ecognine methyl ester were not present in the samples, which suggests that the metabolism of cocaine in the premature neonate is limited.

A room-temperature molecular/organic-based magnet.

The reaction of bis(benzene)vanadium with tetracyanoethylene, TCNE, affords an insoluble amorphous black solid that exhibits field-dependent magnetization and hysteresis at room temperature. The critical temperature could not be estimated as it exceeds 350 kelvin, the thermal decomposition temperature of the sample. The empirical composition of the reported material is V(TCNE)x.Y(CH(2)Cl(2)) with x approximately 2 and Y approximately 1/2. On the basis of the available magnetic and infrared data, threedimensional antiferromagnetic exchange of the donor and acceptor spins resulting in ferrimagnetic behavior appears to be the mode of magnetic coupling.

Conductive polymers derived from iron, ruthenium, and osmium metalloporphyrins: The shish-kebab approach.

The synthesis and characterization of pyrazine-bridged polymers of iron(II/III), ruthenium(II/III), and osmium(II/III) octaethylporphyrin (dubbed "shish-kebab" polymers) are presented. Optical and dc conductivity measurements reveal that the ruthenium and osmium polymers, when partially oxidized, are highly conductive. Electrochemical and ESR results are presented that indicate the existence of an interesting metal-centered conduction pathway. Unlike most of the previously reported porphyrinic molecular metals in which the conduction electrons are macrocyclic-based, electron transport in these materials proceeds exclusively along the metal-pyrazine backbone.