Cl Fragments Research Articles

Phosphine Functionalized CpC Ligands and Their Metal Complexes

Simple nucleophilic aliphatic substitution gives access to mono- and diphosphine ligands with a CpC group in the backbone. The monophosphine ligand coordinates to gold(I) via the phosphine site, to thallium(I) via the cyclopentadienyl site and to ruthenium(II) via a combination of both, resulting in an ansa-type structure. Coordination with the cyclopentadiene site is not possible for the diphosphine ligand. In this case, monodentate coordination to gold(I) and bidentate coordination to the [PdCl(μ2-Cl)]2, the [Rh(CO)(μ2-Cl)]2, and the Rh(CO)Cl fragment is observed, showing the variability in coordination modes possible for the long-chain diphosphine ligand. Ligands and complexes were characterized by means of NMR and IR spectroscopy, elemental analysis and X-ray structure analysis.

Multiple Pathways for Dissociative Adsorption of SiCl4 on the Si(100)-c(4×2) Surface

The adsorption of silicon tetrachloride (STC, SiCl4) on the silicon surface is a crucial process in polysilicon manufacture. However, the underlying mechanism for the adsorption remains highly uncertain. Here, new dissociative adsorption (DA) reaction pathways involving a flip of a silicon dimer in the first layer and considering physisorption are identified. Different DA patterns, inter-row (IR), inter-dimer (ID), and on-dimer (OD), are confirmed by the density functional theory (DFT) calculations at the PBE-D3(BJ)/TZVP-MOLOPT-GTH level. The stable structures for all minima are searched by global optimization through the artificial bee colony (ABC) algorithm. Findings reveal that the parent molecules dissociate first by breaking one Si-Cl bond, following which the resulting SiCl3 and Cl fragments are attached to adjacent Si-atom sites. Moreover, dimer flipping significantly reduces the energy barrier for chemisorption, mainly due to the change in electronic structure that enhances the interaction of the site with the SiCl3 radical. Physisorption may also be accompanied by dimer flipping to form a stable adsorption structure.

A vector correlation study using a hexapole-oriented molecular beam: photodissociation dynamics of oriented isohaloethane.

The photodissociation dynamics of isohaloethane (1-bromo-2-chloro-1,1,2-trifluoroethane) at 234 nm was studied by a sliced imaging technique combined with an oriented molecular beam. The speed and angular distributions of the competitive products of spin-orbit selected Br and Cl atoms were determined by analysis of the obtained images. The anisotropic parameter, β, was found to be 2.0 ± 0.2 for the excited state of Br(2P1/2) (Br*) and 1.2 ± 0.3 for the ground state of Br(2P3/2) (Br). The speed distributions for both Br and Br* exhibited Gaussian-like characteristics. These results indicate that Br atoms were generated by direct formation after excitation through the nσ*(C-Br) potential energy surfaces. In contrast, the angular distributions for the Cl fragments were almost isotropic, while the speed distributions displayed Boltzmann-like characteristics. This suggests that the Cl atoms may form through long-lived parent molecules after photoexcitation. The branching ratio for Br and Cl atom formation was found to be approximately 1.2, that is, Br atom formation occurred preferentially, in contrast to the case of halothane photodissociation reported in our previous work [Che et al., J. Phys. Chem. A, 2020, 124, 5288]. A vector correlation study between the laser polarization axis and the direction of the dipole moment revealed a similar tendency for all photofragments, suggesting that the fragments were formed through a common excited state of isohaloethane. The vector correlation was also studied theoretically for comparison with the experimental results. The angle between the transition dipole moment in photodissociation and the permanent dipole moment was found to be 42 ± 15°. The obtained results indicate that this vector correlation approach combined with an oriented molecular beam is a powerful tool for determining the transition dipole moments in photodissociation.

Future Venus missions and flybys: A collection of possible measurements with mass spectrometers and plasma instruments

This study contains predictions for mass spectrometry and plasma instrument measurements during upcoming Venus flybys of BepiColombo and Solar Orbiter and discusses the possibility of a phosphine detection with mass spectrometry in Venus’ upper atmosphere. The results extend the ones published previously in Gruchola et al. (2019) , where predictions for the proposed ESA mission EnVision and the Venus flyby of JUICE were included. Both the Venus flyby of BepiColombo and the one of Solar Orbiter will take place in August 2021, only 1 day apart. BepiColombo, carrying the neutral mass gas spectrometer STROFIO, could probe the atmosphere around closest approach and obtain data on the thermal and hot neutral particle populations in the upper atmosphere. According to this study, the thermal hydrogen population as well as the hot species H, C, N and O, including isotopes, should be visible to STROFIO. Especially data on the abundance of the hot species would yield important insight into the planetary escape processes. The Solar Orbiter on the other hand carries the plasma instrument SWA-HIS, designed to measure the energetic solar wind ions. During its second Venus gravity assist it will traverse the magnetosheath, the region between bow shock and ion composition boundary, where in addition to the solar wind ions energetic planetary ions are present. The planetary pickup ions can be measured by SWA-HIS, providing important information on the outflow of planetary ions and the ionization processes in the upper atmosphere itself. The recent reports of phosphine in Venus’ cloud decks with an abundance of 20 ppb at 80 km probably overestimate the actual PH 3 abundance, as the data are currently being reanalyzed (Greaves et al., 2021). However, even with this upper limit of 20 ppb a phosphine detection with a mass spectrometer e.g. on-board ESA’s proposed EnVision mission, seems unlikely. To resolve the PH 3 peak and the 16 O 18 O peak a mass resolution of almost 10’000 is required, and the PH 2 D peak is masked by the Cl fragment peak of HCl. Furthermore, NGMS on-board Pioneer Venus with a mass resolution of around 440 did most likely not detect phosphine, as it scanned only a few masses in the mass range of interest where more abundant species than phosphine are present.

Investigation of kinetic parameters for ammonium perchlorate thermal decomposition in presence of gCN/CuO by TG-MS analysis and kinetic compensation correction

The desire to develop a benign burn rate modifier for propellants has accentuated polymeric carbon nitride (gCN) as a potential candidate for the thermal decomposition of ammonium perchlorate (AP). Here, we have synthesized composites of leaf-shaped CuO and gCN via a facile sonochemical approach. From DSC analysis, the addition of gCNCuO1 reduced the decomposition temperature of AP by 59°C and increased the heat release by ~ 1.4 times that of pure AP. The kinetics of AP decomposition was well investigated via in-situ TG-MS technique. From evolved gas analysis evolution of NO, Cl, HCl, N2O/CO2, NO2 and Cl2 fragments were detected. The quantitative interpretation of kinetic parameters for AP decomposition was done using Coats-Redfern method and the normalization of E values were carried out by applying Kinetic Compensation Correction (KCC). After normalization, E values were decreased by 17 ​kJ/mol and 18 ​kJ/mol for the first and second stages respectively.

Clustering and multiphoton effects in velocity map imaging of methyl chloride

We have investigated different effects caused by clustering and multiphoton processes in the photodissociation of CHCl using velocity map imaging (VMI). Single-photon dissociation of CHCl at 193.3 nm yields CH and Cl fragments probed subsequently by resonance enhanced multiphoton ionisation (REMPI) at 333.52 nm and 235.31 nm, respectively. In the clusters, the CH fragments are strongly ‘caged’ losing most of their kinetic energy. Consequently, the VMI is dominated by a sharp central peak. On the other hand, the Cl fragments lose a broad range of energies in the cluster, yielding a blurred isotropic ‘central blob’ in VMI. At an increased 193 nm photon flux, another central feature appears in the CH images for isolated CHCl molecules. This ‘hour-glass’ shaped image corresponds to the CHCl multiphoton ionisation at 193 nm and subsequent CHCl ion photodissociation at 333 nm. The ion photodissociation is a parallel process with the anisotropy β-parameter values between +1.3 and +2.0. The total kinetic energy release (TKER) distribution suggests a high CH vibrational excitation. The CHCl ion photodissociation is discussed and compared to the photodissociation of similar CHBr ion.

Different Dynamics of CH3 and Cl Fragments from Photodissociation of CH3Cl in Clusters.

We investigate the photodissociation of CH3Cl at 193.3 nm using the velocity map imaging technique in (CH3Cl)n clusters in comparison with isolated molecules. Our results for the isolated molecules are in excellent agreement with the previous study of Cl fragments, and we extend it by detecting also the CH3(ν = 0) fragments. For the clusters, the Cl (and Cl*) and CH3 fragment images are dominated by intense central isotropic features. The corresponding kinetic energy distributions (KEDs) reveal significant differences in the CH3 and Cl fragment dynamics. While the CH3 fragments exhibit a very narrow near-zero kinetic energy peak, pointing to almost complete caging of CH3 fragments, the Cl (and Cl*) fragments show more structured KEDs extending all the way to the maximum available kinetic energy. The Cl KED spectra have a bimodal character with two broad peaks close to zero and around 0.6 eV. We observe a higher ICH3(ν=0)/ICl signal ratio from the clusters compared to the monomers. This is attributed to an efficient quenching of the higher vibrationally excited ν2 states of the CH3 fragments generated in the photodissociation. Collisional quenching of these excited states in clusters enhances the detected CH3(ν = 0) state. Finally, we determine the [Cl*]/[Cl] branching ratio for the photodissociation pathways in the clusters as ≈0.55 ± 0.15 compared to 0.86 for the isolated molecules, which is also attributed to the collisional quenching of the excited state in the clusters. The clusters and photofragment dynamics are discussed.

A novel humanized anti-PD-1 monoclonal antibody potentiates therapy in oral squamous cell carcinoma.

Currently, immune checkpoint inhibitors have been shown to extend the survival of many cancer patients. However, few studies have focused on immune checkpoint inhibition for the treatment of patients with oral squamous cell carcinoma (OSCC). Here, by screening at an early stage, we obtained a strain of anti-PD-1 monoclonal antibody (mAb) that targets programmed cell death-1 (PD-1) does not contain the CH1 and CL fragment. In this study, the role of our novel mAb was tested in the treatment of OSCC in vitro and in vivo. We found that our novel mAb can significantly augment T cell mediated cytokine secretion, target cellular lytic and apoptotic abilities, and inhibit tumor growth and inflammation in vivo. The PD-L1 blockade was accompanied by the inhibition of AKT and ERK1/2, thus suggesting that the PD-L1/PD-1 signaling pathway may play an important immunopreventive role in the tumorigenic properties of OSCC cells by modulating the AKT and ERK1/2 pathways. Additionally, PD-L1 staining was observed both in human OSCC tissues and normal oral mucous tissue adjacent to the tumor, which occurred at different rates. Taken together, these results indicated that our novel anti-PD-1 mAb may be used as a clinical therapy in human OSCC development and progression.

Photochemistry of CF3Cl: Quenching of Charged Fragments Is Caused by Nonadiabatic Effects.

For the first time, high-level multireference electronic structure calculations have been performed to study the photochemistry of CF3Cl, allowing a comprehensive interpretation and assignment of experimental data concerning fluorescence, ion-pair formation, and generation of CF3 fragments in several electronic states. All studied dissociation channels correlate either with Cl or Cl- in the ground state. On the other hand, a CF3 fragment can be generated either in the ground or excited state. A rationalization for the nonadiabatic relaxation of CF3Cl, including the formation of an (n4s) stable state and internal conversion at multiple-state intersections, has been provided. Our results explain the anomalous quenching of a charged fragment after low-energy excitation, a fact experimentally observed by separate groups. We show that the CF3+···Cl- ion pair undergoes an internal conversion to the ground state, producing neutral CF3 and Cl fragments. The results also allow understanding as to why CF3Cl is usually a nonemitting species and how UV emission could be induced.

(Invited) Speciation during Wet Etching of III-V Semiconductors

III-V materials could be a substitute for Si and Ge in semiconductor device development because they possess higher carrier mobilities. Wet chemical cleaning and patterning of III-Vs produces soluble species that can remain in the liquid phase, precipitate as solids and remain on the surface, or evaporate as gases. Because etching products contain elements such as In, As, and Sb, they can pose health risks during industrial wafer processing. To better understand the products generated from III-V etching, vapor-phase arsenic levels were measured above wet etching solutions commonly used to clean or etch GaAs. A differentially pumped mass spectrometer system was used to sample the vapor above the etching solution at atmospheric pressure. The mass fragments detected as a function of time were used to determine the arsenic species present and estimate concentrations. Mass fragments corresponding to AsO+, AsH2 + and AsH3 + were detected above GaAs immersed in aqueous HF at room temperature. The partial pressure of the etching products was on the order of 0.1 mTorr. Using N2as a reference, the total gas-phase arsenic concentration above 0.6 M and 28.9 M aqueous HF was approximately 1 ppm and 2 ppm, respectively. These concentrations are about 400 times the Permissible Exposure Limit (PEL) set by the Occupational and Safety Health Administration (OSHA) for inorganic arsenic species. Gallium was not detected in the vapor phase. Inductively-coupled plasma mass spectrometry (ICP-MS) was used to measure etching species in solution. The Ga concentration was higher than that of As by a factor of 100. Combining these techniques, a mass balance was closed between liquid and vapor phase arsenic species within approximately 1 nmol. Etching GaAs in aqueous SC-2 (HCl and H2O2 in DI water) solutions produced AsO+, AsH2 + and AsH3 + in the vapor phase. The total gas-phase arsenic concentration above SC-2 was 5 nmol (about 4 mg/m3) regardless of the reactant concentration. The concentration of AsO+ increased by a factor of 2 when vapor was collected for 30 min prior to measurement. One interpretation is that etching produces AsCl3 which hydrolyzes readily in the liquid or gas phase. To test this hypothesis, arsenic species were examined as a function of time above a GaAs coupon in partially aqueous SC-2 (HCl:H2O2:H2O:CH3OH, 4:3:12:250 v/v). Figure 1 shows mass spectra after pulses of product gases were sampled above the solution. The total gas-phase arsenic concentration increased by a factor of 3.3 when GaAs was etched in partially aqueous SC-2. The primary arsenic fragment was As+, and Cl+ increased by a factor of 5 with respect to GaAs etched in aqueous SC-2. The comparison of As and Cl fragments detected to known cracking patterns supports the hypothesis that AsCl3is produced during etching of GaAs and is hydrolyzed. Speciation of etching products will be compared to OSHA PEL standards for inorganic arsenic species to identify potential hazards present in III-V manufacturing. Figure 1

Synthesis of pillar[5]arenes with a PH-containing fragment

The reactions of phosphorus(III) chloride and 2-chloro-1,3,2-dioxaphospholane with monohydroxypillar[5]arene afforded for the first time the corresponding PH-phosphonates. It was found that the newly formed P–O(Ar) bond is characterized by considerably reduced reactivity, which was rationalized by essential shielding of the phosphorus atom by the pillar[5]arene macrocycle. The pillar[5]arene scaffold stabilizes the highly reactive PIII–Cl fragment, so that the formation of macrocyclic dichlorophosphite can be detected under normal conditions.

Deep-core photoabsorption and photofragmentation of tetrachloromethane near the Cl K-edge.

The fragmentation of the tetrachloromethane molecule following core-shell photoexcitation and photoionization in the neighborhood of the chlorine K-edge has been studied by using time-of-flight mass spectroscopy and monochromatic synchrotron radiation. Branching ratios for ionic dissociation were derived for all the detected ions, which are informative of the decay dynamics and photofragmentation patterns of the core-excited species. In addition, the absorption yield has been measured with a new assignment of the spectral features. The structure that appears above the Cl 1s ionization potential in the photoionization spectrum has been ascribed to the existing connection with electron-CCl4 scattering through experimental data and calculations for low-energy electron-molecule cross sections. In addition, the production of the doubly ionized Cl fragment, Cl2+, as a function of the photon energy has been analysed in the terms of a simple and an appealing physical picture, the half-collision model.

The non-isomorphous crystal structures of NHC-Au-Cl and NHC-Au-Br (NHC is 1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene).

Gold monochloride and monobromide can be transformed into monomeric complexes by ligands such as CO, PPh3 or Me2S, and such ligand-stabilized gold monochloride compounds have been investigated as catalysts, luminescent materials and anticancer drugs, especially when coordinated to a lipophilic benzyl-substituted N-heterocyclic carbene (NHC) ligand. The triclinic structures of NHC-Au-Cl {chlorido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)gold, [AuCl(C29H24N2)]} and NHC-Au-Br {bromido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)gold, [AuBr(C29H24N2)]}, determined by X-ray crystallography at 100 K, have one and four molecules, respectively, in their asymmetric units. The chloride compound shows an almost linear C-Au-Cl fragment [179.76 (8)°], with an Au-C distance of 1.976 (3) Å and an Au-Cl distance of 2.3013 (6) Å, while the bromide compound shows surprisingly large geometry deviations, from 1.969 (12) to 2.016 (10) Å for the Au-C distance and from 2.4279 (14) to 2.4796 (12) Å for the Au-Br distance, in the four independent molecules.

ChemInform Abstract: Regulation of Nonadiabatic Processes in the Photolysis of Some Carbonyl Compounds

AbstractReview: 83 refs.

Regulation of nonadiabatic processes in the photolysis of some carbonyl compounds.

Carbonyl compounds studied are confined to acetyl halide (CH3COCl), acetyl cyanide (CH3COCN), acetyl sulfide (CH3COSH), acetaldehyde (CH3CHO), and methyl formate (HCOOCH3). They are asymmetrically substituted, but do not follow the well-known Norrish type I reactions. Each compound ejected in an effusive beam at about 300 K is commonly excited to the (1)(n, π*)CO lower state; that is, a nonbonding electron on O of the C[double bond, length as m-dash]O group is promoted to the antibonding orbital of π*CO. The photolysis experiments are conducted in the presence of Ar gas and the corresponding fragments are detected using time-resolved Fourier-transform Infrared (FTIR) emission spectroscopy. The enhancement of the collision-induced internal conversion or intersystem crossing facilitates the dissociation channels via highly vibrational states of the ground singlet (So) or triplet (T1) potential energy surfaces. In this manner, an alternative nonadiabatic channel is likely to open yielding different products, even if the diabatic coupling strength is strong between the excited state and the neighboring state. For instance, the photodissociation of CH3COCl at 248 nm produces HCl, CO, and CH2 fragments, in contrast to the supersonic jet experiments showing dominance of the Cl fragment eliminated from the excited state. If the diabatic coupling strength is weak, dissociation proceeds mainly through internal conversion, such as the cases of CH3COCN and CH3COSH. The photodissociation of CH3COCN at 308 nm has never been reported before, while for CH3COSH matrix-isolated photodissociation was conducted that shows a distinct spectral feature from the current FTIR method. The CH3CHO and HCOOCH3 molecules belong to the same type of carbonyl compounds, in which the molecular products, CO + CH4 and CO + CH3OH, are produced through both transition state and roaming pathways. Their products are characterized differently between molecular beam and current FTIR experiments. For instance, the photodissociation of HCOOCH3 at 248 nm yields CO with the vibrational state v ≥ 4, in contrast to the molecular beam experiments producing CO at v = 1. The photodissociation of CH3CHO at 308 nm intensifies a low energy component in the CH4 vibrational distribution, thus verifying the transition state pathway for the first time.

Crystal structure of 4,8-di-tert-butyl-6,6-di-chloro-13-ethyl-2,10-dimethyl-13,14-di-hydro-12H-dibenzo[d,i][1,3,7,2]dioxaza-silecine toluene 0.25-solvate.

The coordination polyhedron at the silicon atom in the title compound, C26H37Cl2NO2Si·0.25C7H8, is typical for penta­coordinated silicon derivatives and represents a slightly distorted trigonal bipyramid with an N atom and a Cl atom in the apical positions and the two O atoms and the other Cl atom occupying the equatorial sites. There are two independent mol­ecules in the asymmetric unit. The N–Si–Cl fragment in each is close to linear [178.24 (5) and 178.71 (5)°], in good agreement with 4e–3c theory, as is the elongation of the apical bond lengths [Si—Cl = 2.1663 (7) and 2.1797 (7) Å] in comparison with the equatorial bonds [Si—Cl = 2.0784 (7) and 2.0748 (7) Å]. Orthogonal least-squares fitting of the two independent mol­ecules resulted in r.m.s. deviation of 0.017 Å. The conformations of the two mol­ecules are almost the same, with corresponding torsion angles differing by less than 5.5°. The toluene solvent mol­ecule is disordered about an inversion centre.

A new linear bismuth coordination polymer based on 1,10-phenanthroline-2,9-dicarboxylic acid: ionothermal synthesis, crystal structure and fluorescence properties.

A new linear bismuth(III) coordination polymer, catena-poly[[chloridobismuth(III)]-μ3-1,10-phenanthroline-2,9-dicarboxylato-κ(6)O(2):O(2),N(1),N(10),O(9):O(9)], [Bi(C14H6N2O4)Cl]n, has been obtained by an ionothermal method and characterized by elemental analysis, energy-dispersive X-ray spectroscopy, IR spectroscopy, thermal stability studies and single-crystal X-ray diffraction. The structure is constructed by Bi(C14H6N2O4)Cl fragments in which each Bi(III) centre is seven-coordinated by one Cl atom, four O atoms and two N atoms. The coordination geometry of the Bi(III) cation is distorted pentagonal-bipyramidal (BiO4N2Cl), with one bridging carboxylate O atom and one Cl atom located in the axial positions. The Bi(C14H6N2O4)Cl fragments are further extended into a one-dimensional linear polymeric structure via subsequent but different centres of symmetry (bridging carboxylate O atoms). Neighbouring linear chains are assembled via weak C-H···O and C-H···Cl hydrogen bonds, forming a three-dimensional supramolecular architecture. Intermolecular π-π stacking interactions are observed, with centroid-to-centroid distances of 3.678 (4) Å, which further stabilize the structure. In addition, the solid-state fluorescence properties of the title coordination polymer were investigated.

Gas‐Phase Fragmentation Reactions of Keggin‐Type {PW11O39M} (M = Rh, Ir, and Ru) Polyoxometalates as Fingerprints of the Ligands Attached at the Noble Metal Site

AbstractThe gas‐phase fragmentation reactions of Keggin‐type [PW11O39MCl]5– (M = Rh, Ir) polyoxometalates (POMs) featuring chloride terminal ligands have been investigated. Different adducts of the general formulas [PW11O39MCl + 2cat]3– and [PW11O39MCl + 3cat]2– [cat = alkylammonium cations (Me4N+, Bu4N+), alkali cations (Na+, K+) or protons] were subjected to collision‐induced dissociation (CID) conditions. The (cat)Cl (cat = H+, Na+ or K+) fragments were released as a common fragmentation pathway and were taken as a fingerprint of the ligands attached at the noble metal site. Other {PW11O39ML} POMs (M = Rh, Ir) with L = thiocyanate, nitrite, methyl, phenylacetate or phenyl were identified on the basis of CID experiments. Coordination studies of thiocyanate anions and CO to {PW11O39Ru} POMs to yield the new compounds [PW11O39RuSCN]5– and [PW11O39RuCO]4– are also reported. CID experiments were also used to validate that thiocyanate and CO ligation at the Ru metal site had occurred.

Clustering and Photochemistry of Freon CF2Cl2 on Argon and Ice Nanoparticles

The photochemistry of CF2Cl2 molecules deposited on argon and ice nanoparticles was investigated. The clusters were characterized via electron ionization mass spectrometry, and the photochemistry was revealed by the Cl fragment velocity map imaging after the CF2Cl2 photodissociation at 193 nm. The complex molecular beam experiment was complemented by ab initio calculations. The (CF2Cl2)n clusters were generated in a coexpansion with Ar buffer gas. The photodissociation of molecules in the (CF2Cl2)n clusters yields predominantly Cl fragments with zero kinetic energy: caging. The CF2Cl2 molecules deposited on large argon clusters in a pickup experiment are highly mobile and coagulate to form the (CF2Cl2)n clusters on ArN. The photodissociation of the CF2Cl2 molecules and clusters on ArN leads to the caging of the Cl fragment. On the other hand, the CF2Cl2 molecules adsorbed on the (H2O)N ice nanoparticles do not form clusters, and no Cl fragments are observed from their photodissociation. Since the CF2Cl2 molecule was clearly adsorbed on (H2O)N, the missing Cl signal is interpreted in terms of surface orientation, possibly via the so-called halogen bond and/or embedding of the CF2Cl2 molecule on the disordered surface of the ice nanoparticles.

Photodissociation Dynamics of Benzoyl Chloride at 235 nm: Resonance-Enhanced Multiphoton Ionization Detection of Cl and HCl

The photodissociation dynamics of benzoyl chloride at 235 nm has been investigated and compared with that of 2-furoyl chloride. Atomic Cl and molecular HCl channels have been detected in benzoyl chloride by employing resonance-enhanced multiphoton ionization technique and time-of-flight mass spectrometry. Both the Cl fragments, Cl((2)PJ=3/2, relative quantum yield 0.70 ± 0.15) and Cl*((2)PJ=1/2), show isotropic angular distribution and bimodal translational energy distributions. The predominant high kinetic energy channel contributes 72% to the C-Cl bond scission and arises from the S1 state having nπ* character of benzoyl chloride. However, the low-energy Cl and HCl channels originate from the ground electronic state. The most plausible mechanism of HCl formation is proposed based on molecular orbital calculations. In contrast to benzoyl chloride, the HCl channel is not observed in 2-furoyl chloride on excitation at 235 nm, and this is attributed to an energy constraint.