We have observed ferromagnetism in dilute (∼1–4at.%) Mn-doped crystalline ZnO nanowires at temperatures up to 400K. Arrays of freestanding single crystal ZnO:Mn nanowires were fabricated by Au-catalyzed vapor-liquid-solid growth. Structure and compositional analyses revealed that Mn was incorporated into the ZnO lattice. From the observed saturation magnetization, the magnetic moment per Mn atom is estimated to be between 0.3μB and 1.2μB. Photoluminescence measurements show a strong suppression of defect related midgap emission, indicative of an interplay between Mn doping and native point defects.
Irradiation of (7,4-C4H4)Fe(CO)3, (r,6-C5Hs)Mn(CO)3, (r,5-C5Me6)Mn(CO)3, (776-C5HB)Re(CO)3, and ( 6-C6H6)Cr(CO)3 leads to dissociative CO loss to form 16e dicarbonyl species. At low temperatures, 85-157 K, the unsaturated dicarbonyl molecules can be spectroscopically (DR) characterized in inert organic solvents, such as methylcyclohexane or 3-methylpentane. In the presence of R3SiH the dicarbonyl species react to form 18e oxidative addition products of the formula (i7n-C"R")MH(SiR3)(CO)2. For all dicarbonyl species the rate of reaction with Et3SiH was investigated. For the Fe and two Mn species a complete study of rate vs. temperature was made. The Cr species reacts too fast to measure quantitatively. The reaction of Et3SiH with the Re species occurs only above 157 K, and detailed studies were not made. The results give an overall reactivity trend for the dicarbonyls toward neat Et3SiH at 100 K of Cr > Mn > Fe > Re and C6Me5 > C5H5. The difference in rate with C6Me5 vs. C5H5 is a factor of ~101 2 over a wide temperature range, and the difference between Cr and Re at 100 K is at least 104. The reactivities of various silanes toward (7?5-C6H6)Mn(CO)2 were also investigated as a function of temperature. The activation parameters, AH* and AS*, show only modest variation with silane such that AH* EtMe2SiH (25 ± 1 kJ mol"1) < Ph3SiH (28 ± 1 kJ mol"1) < t-Pr3SiH (29 ± 1 kJ mol"1 4)< n-Pr3SiH (30 ± 1 kJ mol'1) ~Et3SiH (30 ± 1 kJ mol"1) and AS* Et3SiH (-28 ± 5 J K'1 mol"1) < n-Pr3SiH (-31 ± 5 J K'1 mol"1) = Ph3SiH (-31 ± 5 J K'1 mol"1) < i-Pr3SiH (-33 ± 5 J K"1 mol"1) < EtMe2SiH (-40 ± 5 J K"1 mol"1).
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