Infrared Spectroscopic Characterization of Early 4d Transition Metal Carbene Cations, ZrCH and NbCH.

IR multiple-photon dissociation (IRMPD) action spectroscopy is combined with quantum chemical calculations to examine the [M,C,2H] species for the early 4d metals, M = Zr and Nb. These ions were formed by reacting laser ablated M ions with cyclopropane (-CH) in a molecular beam apparatus. Both IRMPD spectra exhibit one major band near 700 cm and a second weaker band at about twice that wavenumber, more evident when irradiated in focus.

Combining Viedma Ripening and Temperature Cycling Deracemization.

While much data are available for the Viedma ripening and temperature cycling deracemization processes, not much is known about the advantages (or disadvantages) of a combination of the two. We here try to elucidate what happens when Viedma ripening is used in combination with temperature cycling by comparing not only the deracemization times but also the change in the sizes of the crystals. We found that, in the case of NMPA (-(2-methylbenzylidene)-phenylglycine amide) as a model compound, combined experiments significantly increase the deracemization time.