David G. Churchill

The overall reductive elimination of RH from the ansa-molybdenocene and -tungstenocene complexes [Me(2)Si(C(5)Me(4))(2)]Mo(Ph)H and [Me(2)Si(C(5)Me(4))(2)]W(R)H (R = Me, Ph) is characterized by an inverse primary kinetic isotope effect (KIE) for the tungsten system but a normal KIE for the molybdenum system. Oxidative addition of PhH to [[Me(2)Si(C(5)Me(4))(2)]M] also differs for the two systems, with the molybdenum system exhibiting a substantial intermolecular KIE, while no effect is observed

Access to the [Me2Si] ansa-bridged permethylmolybdenocene system is provided by the synthesis of [Me2Si(C5Me4)2]MoCl2 from the reaction of MoCl5 with a mixture of [Me2Si(C5Me4)2]Li2 and NaBH4, followed by treatment with CHCl3. Comparison with the chemistry of the non-ansa Cp*2MoX2 system indicates that incorporation of the [Me2Si] ansa bridge promotes intermolecular C−H and C−C bond activation reactions.

A phenyl-selenium-substituted coumarin probe was synthesized for the purpose of achieving highly selective and extremely rapid detection of glutathione (GSH) over cysteine (Cys)/homocysteine (Hcy) without background fluorescence. The fluorescence intensity of the probe with GSH shows a ∼100-fold fluorescent enhancement compared with the signal generated for other closely related amino acids, including Cys and Hcy. Importantly, the substitution reaction with the sulfhydryl group of GSH at the 4-p

Real-time strategy video games have proven to be a very challenging area for applications of artificial intelligence research. With their vast state and action spaces and real-time constraints, existing AI solutions have been shown to be too slow, or only able to be applied to small problem sets, while human players still dominate RTS AI systems. This paper makes three contributions to advancing the state of AI for popular commercial RTS game combat, which can consist of battles of dozens of uni

Heuristic search has been very successful in abstract game domains such as Chess and Go. In video games, however, adoption has been slow due to the fact that state and move spaces are much larger, real-time constraints are harsher, and constraints on computational resources are tighter. In this paper we present a fast search method — Alpha-Beta search for durative moves— that can defeat commonly used AI scripts in RTS game combat scenarios of up to 8 vs. 8 units running on a single core in under

Two closely related phenyl selenyl based boron-dipyrromethene (BODIPY) turn-on fluorescent probes for the detection of hypochlorous acid (HOCl) were synthesized for studies in chemical biology; emission intensity is modulated by a photoinduced electron-transfer (PET) process. Probe 2 intrinsically shows a negligible background signal; however, after reaction with HOCl, chemical oxidation of selenium forecloses the PET process, which evokes a significant increase in fluorescence intensity. The fl

In recent years, real-time strategy (RTS) games have gained interest in the AI research community for their multitude of challenging subproblems — such as collaborative pathfinding, effective resource allocation and unit targeting, to name a few. In this paper we consider the build order problem in RTS games in which we need to find concurrent action sequences that, constrained by unit dependencies and resource availability, create a certain number of units and structures in the shortest possibl

Detection of nerve agent-related molecules based on BODIPY-salicylaldehyde oxime conjugation was studied. Fluorescence intensity of the B-SAL-OXIME species increases in the presence of DECP, whereas it decreases in the presence of DCP and DEMP (limit of detection = 997 nM). Benzonitrile formation in the novel fluorescent B-SAL-OXIME system was elucidated using model substrates.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTModeling Aspects of Hydrodesulfurization at Molybdenum: Carbon−Sulfur Bond Cleavage of Thiophenes by Ansa Molybdenocene ComplexesDavid G. Churchill, Brian M. Bridgewater, and Gerard ParkinView Author Information Department of Chemistry, Columbia University New York, New York 10027 Cite this: J. Am. Chem. Soc. 2000, 122, 1, 178–179Publication Date (Web):December 23, 1999Publication History Received11 October 1999Published online23 December 1999Pub

In recent decades, HOCl research has attracted a lot of scientists from around the world. This chemical species is well known as an important player in the biological systems of eukaryotic organisms including humans. In the human body, HOCl is produced by the myeloperoxidase enzyme from superoxide in very low concentrations (20 to 400 μm); this species is secreted by neutrophils and monocytes to help fight pathogens. However, in the condition called "oxidative stress", HOCl has the capability to

A new 1,8-naphthalimide-based fluorescent probe for the detection of diethyl cyanophosphonate, a very common nerve agent simulant, is designed, synthesized, and characterized fully. The probe shows around 50-fold enhancement of fluorescence intensity over other nerve agent simulants. Importantly, the probe is able to work under aqueous conditions in a wide pH range. Two reactive groups, the oxime and the phenol, allow a dual emission with different kinetic reactions. The reaction of diethyl cyan

Every chemical research laboratory probably contains some form of explosion hazard. Clearly defining the molecular structure of energetic materials, especially those with trivial names, helps spot danger. Depiction of critical chemical functionality is useful for beginning preparative chemistry students and helpful in stimulating laboratory safety discussions. Here, common classes of hazardous substances (and physical explosions) are illustrated and briefly discussed: nitro, hydrazido, and azido

Small-molecule organoselenium-based fluorescent probes possess great capacity in understanding biological processes through the detection of various analytes such as reactive oxygen/nitrogen species (ROS/RNS), biothiols (cysteine, homocysteine and glutathione), lipid droplets, etc. Herein, we present how substituents on the BODIPY system play a significant part in the detection of biologically important analytes for in vitro conditions and live cell imaging studies. The fluorescence of the probe

A novel rechargeable meso-aryl Bodipy-based Cys sensing ensemble has been developed (“turn on,” ΦF = <0.05 → 0.72, limit of detection = 6.0 × 10−6 M) with exceptional selectivity over homocysteine, N-acetylcysteine, glutathione (GSH) and methionine.