No abstract

Herein we report the employment of the quintuply bonded dichromium amidinates [Cr{k 2 -HC(N-2,6i Pr 2 C 6 H 3 )(N-2,6-R 2 C 6 H 3 )}] 2 (R = iPr (1), Me (7)) as catalysts to mediate the [2+ +2+ +2] cyclotrimerization of terminal alkynes giving 1,3,5-trisubstituted benzenes.D uring the catalysis,t he ultrashort Cr À Cr quintuple bond underwent reversible cleavage/formation, corroborated by the characterization of two inverted arene sandwich dichromium complexes (m-h 6 :h 6 -1,3,5-(Me 3 Si) 3 C 6 H 3 )[Cr{k 2 -HC(N-2,6-i Pr 2 C 6 H 3 )(N-2,6-R 2 C 6 H 3 )}] 2 (R = i Pr (5), Me (8)). In the presence of s donors,such as THF and 2,4,6-Me 3 C 6 H 2 CN,t he bridging arene 1,3,5-(Me 3 Si) 3 C 6 H 3 in 5 and 8 was extruded and 1 and 7 were regenerated. Theoretical calculations were employed to disclose the reaction pathwayso ft hese highly regioselective [2+ +2+ +2] cylcotrimerization reactions of terminal alkynes. Scheme 2. Reversible cleavage/formation of the CrÀCr quintuple bond in the cyclotrimerization of Me 3 SiCCH. Scheme 3. No cross reactions between 5 and 8 in THF.

No abstract

The purpose of this project is to design and implement a portable yet high resolution color sensor which can identify the color, and can discern the color difference between a new paint and the old one. The resolution is 1/256 in digit. This device can give the provider a handful tool to get the right color of paint when body job is needed. Also, this device can ensure customers their paint jobs are well carried out with the objective digital readout from the device. This device uses the infrared photodiode pair as the color sensor. One constant current source with feedback loop from one photodiode receiver to ensure a pre-fixed brightness of infrared light is emitted from the transmitter. Another photodiode picks up the reflected signal from surface in a pre-determined distance. The color difference can be seen as the amplitude variation of the reflected signal. This amplitude variation then feeds into A/D converter to quantifilize the color into digits, i.e. 0 to 255 in the resolution of 1/256. A single chip microprocessor takes in the information via its I/O port and compares the data with a built-in color look-up table. Finally, the identified color along with its digitalized brightness readout is shown on a LCD display controlled by the micro-processor to carry out the color scrutiny scheme.