Mechanistic understanding of mechanochemical reactions is sparse and has been acquired mostly by stepwise ex situ analysis. We describe herein an unprecedented laboratory technique to monitor the course of mechanochemical transformations at the molecular level in situ and in real time by using Raman spectroscopy. The technique, in which translucent milling vessels are used that enable the collection of a Raman scattering signal from the sample as it is being milled, was validated on mechanochemical reactions to form coordination polymers and organic cocrystals. The technique enabled the assessment of the reaction dynamics and course under different reaction conditions as well as, for the first time, direct insight into the behavior of liquid additives during liquid‐assisted grinding.

Monitoring of mechanochemical thiocarbamoylation by in situ Raman spectroscopy revealed the formation of aryl N-thiocarbamoylbenzotriazoles, reactive intermediates deemed unisolable in solution. The first-time isolation and structural characterization of these elusive molecules demonstrates the ability of mechanochemistry to access otherwise unobtainable intermediates and offers a new range of masked isothiocyanate reagents.

COMMUNICATIONThe first direct mechanochemical transition-metal-mediated activation of strong phenyl C-H bonds is reported. Mechanochemical procedure, resulting in cyclopalladated complexes, is quantitative and significantly faster than solution synthesis and allows highly regioselective activation of two C-H bonds by palladium(II) acetate in asymmetrically substituted azobenzene. Milling is monitored by in situ solidstate Raman spectroscopy and in combination with quantumchemical calculations enabled characterization of involved reaction species, direct insight into the dynamics and reaction pathways, as well as the optimization of a milling process.Cyclometalation via the transition-metal-mediated activation of carbon-hydrogen (C-H) bond is the simplest and the most common method for the formation of a metal-carbon (M-C) σ bond. 1 After the first reports in the middle 1960s, 2 the C-H activation process remains the most straightforward method for preparation of cyclometalated compounds which are widely used in organic synthetic chemistry for the insertion of various functionalities into hydrocarbons. 3 Among them, cyclopalladated compounds have been studied most extensively not only for their wide application in organic synthesis and catalysis, but also due to their mesogenic, bioactive and photoluminescent properties. 1a,1c,4 The synthesis of all known metalacycles relies exclusively on solvent-based techniques which may require elevated temperatures, toxic solvents (benzene, toluene, chloroform) and are often time-consuming. 1a,1c,4 During the last decade mechanochemical reactions emerged as a viable and environmentally-friendly alternative to solvent-based techniques. 5 Apart from the processing of inorganic materials, 6 mechanosynthesis has been recognized as a rapid, selective and atom-and energy-efficient pathway to various classes of compounds Ruđer Bošković Institute, Bijenička 54, HR-10000 Zagreb, Croatia E-mail: curic@irb.hr †Electronic Supplementary Information (ESI) available: Experimental and computational details. CCDC 1005635-1005636 For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4cc04423a ‡ These authors contributed equally to this work.ranging from organic molecules 7 and cocrystals 8 up to metal-organic coordination compounds. 9 Despite its wide application in different areas of chemistry, solid-state synthesis of organometallic compounds by direct formation of a M-C σ bond has not been reported yet.Here we describe the first example of palladium-mediated solidstate C-H bond activation in asymmetrically substituted azobenzene 1, achieved by mechanochemical milling process (Scheme 1). The palladation of 1 proved to be regioselective, producing regioisomer 1A in higher yield and much faster than the analogous reaction in solution, with the reduction of solvent volume more than 10000 times. Further reaction of 1A with palladium(II) acetate (Pd(OAc) 2 ) leads to the second C-H bond activation forming in a quantitative yield the doubly palladated complex 1...

In situ Raman spectroscopy was employed to study the course of a mechanochemical nucleophilic substitution on a carbonyl group. We describe evidence of base catalysis, akin to catalysis in solution, achieved by liquid-assisted grinding.

In this work we investigate operation in the Geiger mode of the new single photon avalanche photo diode (SPAD) SAP500 manufactured by Laser Components. This SPAD is sensitive in the range 400-1000nm and has a conventional reach-through structure which ensures good quantum efficiency at the long end of the spectrum. By use of passive and active quenching schemes we investigate detection efficiency, timing jitter, dark counts, afterpulsing, gain and other important parameters and compare them to the "standard" low noise SPAD C30902SH from Perkin Elmer. We conclude that SAP500 offers better combination of detection efficiency, low noise and timing precision.

Mechanistic understanding of mechanochemical reactions is sparse and has been acquired mostly by stepwise ex situ analysis. We describe herein an unprecedented laboratory technique to monitor the course of mechanochemical transformations at the molecular level in situ and in real time by using Raman spectroscopy. The technique, in which translucent milling vessels are used that enable the collection of a Raman scattering signal from the sample as it is being milled, was validated on mechanochemical reactions to form coordination polymers and organic cocrystals. The technique enabled the assessment of the reaction dynamics and course under different reaction conditions as well as, for the first time, direct insight into the behavior of liquid additives during liquidassisted grinding.

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A series of thin silicon films with different degrees of crystallinity were prepared by decomposition of silane gas highly diluted with hydrogen, in radiofrequency glow discharge. The crystallite size, shape, and the portion of crystalline phase were investigated by highresolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy (RS), and X-ray powder diffraction (XRD). The absorption coefficient (a) was calculated from the measurement of UV-vis-transmittance. By using RS, the volume fractions of the crystalline phase were estimated from the ratio of the integrated intensities of transversal optical (TO)-related crystalline and amorphous bands. These results were in excellent agreement with the mean crystallite sizes measured in HRTEM images and crystallite sizes refined from XRD measurements. The red shift of absorption, appearing as a result of the increase of the crystal fraction, depends on the size and distribution of nanocrystals.