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Department of Chemistry


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Faculty - Howard H. Patterson

The Patterson group carries out research in the areas of inorganic, analytical and environmental chemistry. Specifically, our work is focused in photochemistry/photophysics, the development of fluorescence based methods for detection of water pollutants and photocatalysis of those pollutants. Our group consists of PhD, master, undergraduate and high school student researchers. Below is a summary of the areas of chemistry we are currently exploring.

Ag(I) in its ground state has a d10 closed shell electronic configuration, but when excited has a d9s1 or d9p1 open shell configuration. The result is that when two Ag(I) ions come together in their ground state, the two closed shell ions bond together weakly with a shallow potential well. However, in their excited states, two open shell ions with d9s1 or d9p1 configuration bond strongly with a deep potential well. This situation corresponds to the formation of excimers and exciplexes depending on the number of ions, two or more, respectively. This situation is common in organic chemistry but very uncommon in inorganic chemistry, especially where luminescence occurs. Previously, our research group has reported that when Ag(CN)2- ions are doped in single alkali halide crystals, the luminescence can be tuned over 18000 cm-1 by selective excitation of each emissive excimer and exciplex. We have named this phenomena “exciplex tuning”.

In a collaboration with Professor Daniel Leznoff at Simon Frasier University, we have studied tunable energy transfer from d10 donor exciplex ions to terbium(III) and europium (III) acceptor ions. Exclusive excitation of the host d10 ions leads to photoluminescence from the Eu+3 ion indicating donor to acceptor excited state  energy transfer with the donor emission quenched at all temperatures. Also, pressure dependent studies of Eu[Au(CN)2]3 up to 60 kbar show that as the pressure is increased the HOMO-LUMO separation of the donor is decreased and the gold emission appears and is tunable. Further, we have investigated the metallophilic interactions and tunable photoluminescence for closed shell heterobimetallic dicyanide layered systems.

In a research program with Professor Robert Pike and The College of William and Mary, we have extensively studied the luminescence behavior of Cu(I) cyanide and iodide frameworks exposed to vapor and liquid amines. Binding of these various amine nucleophiles to the copper metal centers modulates unique photophysics that gives rise to a wide range of luminescence responses in the visible range. Different amines induce different colors; in some cases similar amines produce strikingly different colors, making these metal anion motifs potential sensors for amine detection in the environment.

In the area of environmental analytical chemistry we are developing a rapid, in situ screening method for the detection of pharmaceutical and personal care products (PPCP) compounds in natural water samples. Three-dimensional excitation emission (EEM) spectra provide a fluorescence ‘fingerprint’ of a water  sample.  Chemometric techniques, such as parallel factor analysis (PARAFAC), can be used to deconvolute datasets of such spectra and extract chemically relevant information in the presence of a complex background signal.  We utilize the above-mentioned techniques to identify and quantify PPCP contaminants in surface water samples.  17α ethinyl-estradiol (EE2), bisphenol A (BPA) and triclosan have been quantified at environmentally relevant concentrations using this fluorescence spectroscopic method. The overall goal of this research is to use fluorescence EEMs combined with chemometric analysis to detect pollutants in natural waters.

The Patterson research group has a history of using metal doped zeolites to assist in the photocatalysis of various organic pollutants in water. There are two projects current running on the use of such catalysts. One is focused on the breakdown of petroleum and related petrochemicals and another on the degradation of pharmaceuticals and personal care products including EE2 and BPA. The Patterson group currently has a collaboration with Prof. Wei Fan at UMass Amherst  for the synthesis and use of nano-scale zeolites doped with various metals. There is also another working collaboration with Prof. Mohammad Omary’s group at the University of North Texas for the use of Fluorinated-Metal-Organic Frameworks(FMOFs) for the photocatalysis of the previously stated contaminants.

Recent Select Publications:

Li, X.; Zhong, P.; Welch, D.A.; Baril-Robert, F.; Pike, R.D.; and Patterson, H.H. An Unusual Luminescent Anionic Copper(I) System: Dicyanocuprate(I) Ion in Nano and Bulky States. Journal of Physical Chemistry C, 2012, 116 (50), 26656.

Roberts, R.J.; Li, X.; Lacey, T.F.; Pan, Z.; Patterson, H.; Leznoff, D.B. Heterobimetallic Lanthanide-Gold Coordination Polymers: Structure and Emissive Properties of Isomorphous [nBu4N]2[Ln(NO3)4Au(CN)2] 1-D Chains. Dalton Transactions, 2012, 41 (23), 6992.

Abouelwafa, A. S.; Anson, C. E.; Hauser, A.; Patterson, H. H.; Baril-Rober, F.; Powell, A. K. Photophysical Properties of {[Au(CN)2]}2 Dimers Trapped in a Supramolecule Electron-Acceptor Organic Framework. Inorganic Chemistry, 2012, 51(3), 1294.

Safko, J.P.; Kuperstock, J.E.; Mccullough, S.M.; Noviello, A.M.; Li, X.; Killarney, J.P.; Murphy, C.; Patterson, H.H.; Bayse, C.A.; Pike, R.D. Network Formation and Photoluminescence in Copper(I) Halide Complexes with Substituted Piperazine Ligands. Dalton Transactions, 2012, 41(38), 11663.

Wang, Q.; Peckenham, J.; Pinto, J.; Patterson, H. Kinetics and equilibrium properties of the biosorption of Cu2+ by algae. Environmental Science and Pollution Research, 2012, 19(9), 3889.

Charlestra, L.; Amirbahman, A.; Courtemanch, D.L.; Alvarez, D.A.; Patterson, H. Estimating pesticide sampling rates by the polar organic chemical integrative sampler (POCIS) in the presence of natural organic matter and varying hydrodynamic conditions. Environmental Pollution, 2012, 169, 98.

Miller, K. M.; McCullough, S. M.; Lepekhina, E. A.; Thibau, I. J.; Pike R. D.; Li, X.; Killarney, J. P.; Patterson, H. H. “Copper(I) Thiocyanate-Amine Networks: Synthesis, Structure, and Luminescence Behavior”. Inorganic Chemistry, 2011, 50 (15), 7239.

Welch, D. A.; Baril-Robert, F.; Li, X.; Patterson, H. H. Luminescence and Simulation of Mixed Metal Nanoclusters of Dicyanoargentate(I) and Dicyanoaurate(I) in Alkali Halides.  Inorg. Chim. Acta. 2011, 370 (1), 279.

Baril-Robert, F.; Li, X.; Katz, M. J.; Geisheimer, A. R.; Leznoff, D. B.; Patterson, H. H. Changes in Electronic Properties of Polymeric One-Dimensional {[M(CN)2]-}n (M = Au, Ag) Chains due to Neighboring Closed-Shell Zn(II) or Open-shell Cu(II) Ions. Inorg. Chem. 2011, 50, 231

Miller, K. M.; McCullough, S. M.; Lepekhina, E. A.; Thibau, I. J.; Pike R. D.; Li, X.; Killarney, J. P.; Patterson, H. H. “Copper(I) Thiocyanate-Amine Networks: Synthesis, Structure, and Luminescence Behavior”. Inorg. Chem., 2011, 50 (15), 7239.

Baril-Robert, F.; Li, X.B.; Welch, D.A.; Schneider, B.Q.; O’Leary, M.; Larochelle, C.L.; Patterson, H.H. Site-Selective Excitation of “Exciplex Tuning” for Luminescent Nanoclusters of Dicyanoargentate(I) Ions Doped in Different Alkali Halide Crystals. J.Phys.Chem.C. 2010, 41,114, 17401.

Ley, A.N.; Dunaway, L.E.; Brewster, T.P.; Dembo, M.D.; Harris, T.D.; Baril-Robert, F.; Li, X.; Patterson, H.H.; Pike, R.D. Reversible luminescent reaction of amines with copper(I) cyanide. Chemical Communications, 2010, 46, 4565.

Lu, H.; Yson, R.; Li, X.; Larochelle, C.; Patterson, H.H. Luminescent Studies of “Exciplex Tuning” for Nanoclusters of Dicyanocuprate(I) Ions Doped in Potassium Chloride Crystals. The Journal of Physical Chemistry C, 2009, 113 (15), 5952.

Baril-Robert, F.; Guo, Z; Patterson, H.H. Study of the energy transfer process in the highly luminescent heterometallic dimers of Ce3+ and d10 [Ag(CN)2]− or d8 [Pt(CN)4]2− ions, Chemical Physics Letters, 2009, 471, 258.

Image Description: Howard H. Patterson

Image Description: Patterson group picture

Image Description: This image is an excitation emission matrix (EEM) fluorescence spectrum of the synthetic hormone EE2 in an environmental water sample at a 10-6 molar concentration. We are using this technique to take chemical ‘fingerprints’ of natural water samples.

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Department of Chemistry
156 Aubert Hall
Orono, ME 04469
Phone: (207)-581-1169 | Fax: (207)-581-1191
The University of Maine
Orono, Maine 04469
207.581.1110
A Member of the University of Maine System