Composite ab initio CBS-Q and G3 methods were used to calculate the bond dissociation energies (BDEs) of over 200 compounds listed in CRC Handbook of Chemistry and Physics (2002 ed.). It was found that these two methods agree with each other excellently in the calculation of BDEs, and they can predict BDEs within 10 kJ/mol of the experimental values. Using these two methods, it was found that among the examined compounds 161 experimental BDEs are valid because the standard deviation between the experimental and theoretical values for them is only 8.6 kJ/mol. Nevertheless, 40 BDEs listed in the Handbook may be highly inaccurate as the experimental and theoretical values for them differ by over 20 kJ/mol. Furthermore, 11 BDEs listed in the Handbook may be seriously flawed as the experimental and theoretical values for them differ by over 40 kJ/mol. Using the 161 cautiously validated experimental BDEs, we then assessed the performances of the standard density functional (DFT) methods including B3LYP, B3P86, B3PW91, and BH&HLYP in the calculation of BDEs. It was found that the BH&HLYP method performed poorly for the BDE calculations. B3LYP, B3P86, and B3PW91, however, performed reasonably well for the calculation of BDEs with standard deviations of about 12.1-18.0 kJ/mol. Nonetheless, all the DFT methods underestimated the BDEs by 4-17 kJ/mol in average. Sometimes, the underestimation by the DFT methods could be as high as 40-60 kJ/mol. Therefore, the DFT methods were more reliable for relative BDE calculations than for absolute BDE calculations. Finally, it was observed that the basis set effects on the BDEs calculated by the DFT methods were usually small except for the heteroatom-hydrogen BDEs.

A key step in the oxidation of water to O 2 in the catalytic cycle of Photosystem II is the conversion of a MnOH species to MnO. This transformation is proposed to occur through proton-coupled electron transfer (PCET) 1 from the hydroxo ligand to a nearby tyrosyl radical. 2 Examples of this transformation in well-characterized systems are rare. 3 The reverse reaction, in which a hydrogen atom is abstracted from a substrate by a highly reactive metal oxo intermediate, is more commonly observed. 4 Imido ligands, which are often considered to be surrogates for oxos, display similar reactivity. Thus, hydrogen abstraction by imidos is often observed, 5,6 but their formation by PCET from an amido complex has not been reported. 7 Here we describe the formation of a cobalt(III) imido complex from the corresponding cobalt (II) amido complex, and present computational data consistent with a concerted (PCET) pathway.The four-coordinate complex LCoCl 8 (L = phenyltris(1-tertbutylimidazol-2-ylidene)borato) reacts with LiNH t Bu to form the dark green, high spin (S = 3/2) amido complex LCoNH t Bu in high yield. This rare example of a monomeric cobalt amido complex has been crystallographically characterized (Fig. 1a). The asymmetric unit consists of three crystallographically independent molecules, all showing identical structural features. The Co-N bond lengths (1.886(7)-1.88(2) Å) and bent Co-N-C linkages (152.5(2)-172.4(9)°) are comparable to those of other three-and four-coordinate cobalt amido complexes. 9The 1 H NMR spectrum of the complex is consistent with the X-ray crystal structure. Seven paramagnetically shifted resonances are observed and can be assigned on the basis of integration. A weak band at 3149 cm -1 in the IR spectrum is assigned to the N-H stretching vibration. Although sensitive to both water and oxygen, this complex has significantly greater thermal stability than most late transition metal alkylamido complexes, remaining unchanged for days at 100 °C.Reaction of the amido complex with the stable 2,4,6-tri(tert-butyl)phenoxy radical 10 results in immediate formation of the lilac cobalt(III) imido complex LCoN t Bu in high yield (Scheme 1). The diamagnetic cobalt product has been characterized by X-ray crystallography (Fig. 1b) and 1 H NMR spectroscopy, and the 2,4,6-tri(tert-butyl)phenol byproduct has been characterized by 1 H NMR spectroscopy. The X-ray crystal structure of LCoN t Bu shows similar features to related complexes. In particular, the short Co(1)-N(41) bond length (1.660(3) Å) and linear Co(1)-N(41)-C(41) bond angle (179.7(3)°) are in line with other structurally characterized cobalt(III) imidos. 11 This transformation is unique in the synthesis of late metal imido complexes, which are typically prepared via nitrene capture by low valent precursors.jesmith@nmsu.edu. At least three mechanisms for the formation of LCo III N t Bu can be proposed (Scheme 2, the corresponding organic species are not shown). 12 The cobalt(II) amido complex could react by electron transfer (ET) to form an intermed...

Supply voltage reduction with process scaling has made the design of analog, RF and mixed mode circuits increasingly difficult. In this paper, we present the design of an ultra-low voltage, low power and highly integrated dual-mode receiver for 2.4-GHz ISM-band applications. The receiver operates reliably from 0.55-0.65 V and is compatible with commercial standards such as Bluetooth and ZigBee. We discuss the design challenges at low voltage supplies such as limited f T for transistors and higher nonlinearities due to limited available signal swing, and present the architectural and circuit level design techniques used to overcome these challenges. The highly integrated receiver prototype chip contains RF front-end circuits, analog baseband circuits and the RF frequency synthesizer and was fabricated in a standard digital 90-nm CMOS process; it achieves a gain of 67 dB, noise figure of 16 dB, IIP 3 of 10.5 dBm, synthesizer phase noise of 127 dBc/Hz at 3-MHz offset, consumes 32.5 mW from 0.6 V and occupies an active area of 1.7 mm 2 .

A number of lithium bonding systems (X-LiY) have been found in which the X-Li bond is shortened due to the lithium bond formation.