droplet   McNeill Research Group
University of Minnesota • Department of Chemistry


Research Interests: Mechanistic Environmental Chemistry

  Apollo 16Overview

The goal of our research is to understand key chemical processes of current environmental problems including surface water pollution by pharmaceuticals, groundwater pollution by chlorocarbons, and the global carbon cycle.  Specifically, we are focused on the role of reactive oxygen species in environmental photochemical reactions and the catalytic dehalogenation of halocarbons by a range of synthetic metal complexes.  We take a fundamental chemistry-based approach, with a focus on elucidating reaction mechanisms. Our research strategy involves first obtaining a detailed mechanistic understanding of an environmentally important process under simplified laboratory conditions and then assessing the significance of that process under real-world conditions.
Aquatic Photochemistry

Photochemical Production of Reactive Transient Species by Natural Organic Matter

detection scheme


  A major area of interest in our group is the production of reactive oxygen species (ROS) from the photochemical reactions of natural organic matter. Projects in this area include developing detection methods for ROS, studying the spatial distribution of these species in natural waters, and understanding how they interact with their precursor material, natural organic matter. The goal is to develop a detailed understanding of the production, distribution, and behavior of ROS for an improved understanding of their role in the transformations of both pollutants and natural compounds. We collaborate with Prof. Jim Cotner (Univ. of Minnesota, Dept. of Ecology, Evolution and Behavior), an expert on the microbial utilization of dissolved organic carbon (DOC), on coupled photochemical-biochemical degradation pathways for DOC in Lake Superior.

• D. E. Latch, K. McNeill, Microheterogeneity of singlet oxygen distributions in irradiated humic acid solutions, Science 2006, 311, 1743-1747.
• A. L. Boreen, K. McNeill, Photosensitizing properties of 2,4-dichlorobenzoic acid and chlorinated biphenyl carboxylic acids, potentially key components of chromophoric dissolved organic matter, Chem. Commun., 2005, 4113-4115.
• L. A. MacManus-Spencer, K. McNeill, Quantification of singlet oxygen production in the reaction of superoxide with hydrogen peroxide using a selective chemiluminescent probe, J. Am. Chem. Soc. 2005, 127, 8954-8955.
• A. M. McNally, E. C. Moody, K. McNeill, Kinetics and mechanism of the sensitized photodegradation of lignin model compounds, Photochem. Photobiol. Sci. 2005, 4, 268-274.
• L. A. MacManus-Spencer, D. E. Latch, K. M. Kroncke, K. McNeill, Stable dioxetane precursors as selective trap-and-trigger chemiluminescent probes for singlet oxygen, Anal. Chem. 2005, 77, 1200-1205.
Photochemical Reactions of Pharmaceutical Pollutants in Surface Waters

 ppcps A specific application of our interest in ROS in natural waters is their role in the photodegradation of pollutants in surface waters.  Pharmaceutical compounds in surface waters are a recently discovered problem, the scope of which is actively being investigated. Antibiotics and hormones are among the most prominent causes for concern because of their potential to promote environmental antibiotic resistance and to interfere with chemical signaling in fragile ecosystems. Very little is known about the environmental fate of these compounds, but their chemical structures lead us to hypothesize that photochemical processes are important in determining their fate and persistence. In collaboration with Prof. William Arnold (Univ. of Minnesota, Dept. of Civil and Environmental Engineering), we are developing mechanism-based models that will help predict the photochemical lifetimes of pharmaceuticals in natural systems.

• J. J. Werner, W. A. Arnold, K. McNeill, Water Hardness as a Photochemical Parameter: Tetracycline Photolysis as a Function of Calcium Concentration, Magnesium Concentration and pH, Environ. Sci. Technol. 2006, 40, XXXX.
• B. L. Edhlund, W. A. Arnold, K. McNeill, Aquatic photochemistry of nitrofuran antibiotics, Environ. Sci. Technol. 2006, 40, 5422-5427.
• K. H. Wammer, T. M. LaPara, K. McNeill, W. A. Arnold, D. L. Swackhamer, Changes in antibacterial activity of triclosan and sulfa drugs due to photochemical transformations, Env. Toxicol. Chem. 2006, 25, 1480-1486.
• A. L. Boreen, W. A. Arnold, K. McNeill, Triplet-Sensitized Photodegradation of Sulfa Drugs Containing Six-Membered Heterocyclic Groups: Identification of an SO2 Extrusion Photoproduct, Environ. Sci. Technol. 2005, 39, 3630-3638.
• D. E. Latch, J. L. Packer, B. L. Stender, J. VanOverbeke, W. A. Arnold, K. McNeill, Aqueous photochemistry of triclosan: Formation of 2,4-dichlorophenol, 2,8-dichlorodibenzo-p-dioxin and oligomerization products, Environ. Toxicol. Chem. 2005, 24, 517-525.
• J. J. Werner, K. McNeill, W. A. Arnold, Environmental photodegradation of mefenamic acid. Chemosphere 2005, 58, 1339-1346.
• A. L. Boreen, W. A. Arnold, K. McNeill, Photochemical Fate of Sulfa Drugs in the Aquatic Environment: Sulfa Drugs Containing Five-Membered Heterocyclic Groups, Environ. Sci. Technol., 2004, 38, 3933-3940.
• J. L. Packer, J. J. Werner, D. E. Latch, K. McNeill, W. A. Arnold, Photochemical fate of pharmaceuticals in the environment: naproxen, diclofenac, clofibric acid, and ibuprofen, Aquatic Sci. 2003, 65, 342-351.
• A. L. Boreen, W. A. Arnold, K. McNeill, Photodegradation of pharmaceuticals in the aquatic environment: A review, Aquatic Sci. 2003, 65, 320-341.
• D. E. Latch, B. L. Stender, J. L. Packer, W. A. Arnold, and K. McNeill, Photochemical Fate of Pharmaceuticals in the Environment: Cimetidine and Ranitidine. Environ. Sci. Technol. 2003, 37, 3342-3350.
• D. E. Latch, J. L Packer, W. A. Arnold, K. McNeill, Photochemical Conversion of Triclosan to 2,8-Dichlorodibenzo-p-dioxin. J. Photochem. Photobiol. A. 2003, 158, 63-66.
Metal-Catalyzed Dechlorination Reactions
Organometallic Intermediates in Dechlorination Catalysis

chlorovinyl complex
  Another major area of interest is the development and study of catalysts that are capable of degrading chlorocarbons, some of the most abundant organic drinking water pollutants in the US. Our focus is on reactions that remove halogen atoms from these pollutants, because it is the halogens that confer their toxicity and harmful environmental behavior. 

A specific focus area is the intemediacy of metal-carbon bonded organometallic intermediates in these processes. For example, chlorovinylcomplexes of cobalt may be key intermediates in the catalytic dehalogenation of chlorinated ethylenes. We have recently developed a synthetic route into these compounds, and have begun to study their reaction chemistry and possible intermediacy in dehalogenation reactions.

• A. D. Follett, K. McNeill, Evidence for the formation of a cis-dichlorovinyl anion upon reduction of cis-1,2-dichlorovinyl(pyridine)cobaloxime, Inorg. Chem. 2006, 45, 2727-2732.
• J. M. Fritsch, N. D. Retka, K. McNeill, Synthesis, structure, and the unusual reactivity of b‑halovinyl cobalt porphyrin complexes, Inorg. Chem. 2006, 45, 2288-2295.
• J. M. Fritsch, K. McNeill, Aqueous reductive dechlorination of chlorinated ethylenes with tetrakis-(4-carboxyphenyl)porphyrin cobalt, Inorg. Chem. 2005, 44, 4852-4861.
• A. D. Follett, K. McNeill, Reduction of trichloroethylene by outer-sphere electron transfer agents, J. Am. Chem. Soc. 2005, 127, 844-845.
• A. E. Rich, A. D. DeGreeff, K. McNeill, Synthesis of (chlorovinyl)cobaloxime complexes, model complexes of proposed intermediates in the B12-catalyzed dehalogenation of chlorinated ethylenes. Chem. Commun. 2002, 234-235.
Development of New Dechlorination Catalysts

catalytic cycle

  Chlorocarbons, as a class, are the most abundant organic pollutants of drinking water in the US, and the global reservoir of these compounds grows annually as their production rate greatly exceeds their degradation rate. A major goal of our research is to help stem the flow of these pollutants to the environment by developing rapid dechlorination reactions. Specifically, we develop highly active aqueous-phase dechlorination catalysts based upon simple models of naturally occurring catalysts, such as Vitamin B12. 
  The results will lead to improved halocarbon remediation technologies, an improved understanding of the mechanisms of carbon-halogen bond metallation, and insight into natural biogeochemical cycling of halogenated organics.

• A. A. Peterson, K. McNeill, Catalytic Dehalogenation of sp2 C-F and C-Cl Bonds in Fluoro- and Chloroalkenes, Organometallics, 2006, XXXX.
• T. D. DeJournett, J. M. Fritsch, K. McNeill, W. A. Arnold, Preparation of 14C-cis-dichloroethylene from 14C-trichloroethylene using a cobalt porphyrin catalyst, J. Label. Compd. Radiopharm. 2005, 48, 353-357.
• J. M. Fritsch, K. McNeill, Aqueous reductive dechlorination of chlorinated ethylenes with tetrakis-(4-carboxyphenyl)porphyrin cobalt, Inorg. Chem. 2005, 44, 4852-4861.
©2006 Kristopher McNeill