Professor
A. B. 1978, Cornell Univ., M.S. 1980, M. Phil. 1981, Ph.D. 1985, Yale Univ.

Organic, Materials, Computational Chemistry
Production, observation, and chemistry of highly reactive species: computational investigation of reactive species; synthesis of highly conjugated polymers; organic diradicals and polyradicals; crystal engineering; molecular magnetism; organic electroluminescent polymers and materials; bioactivity of phenols.

Department of Chemistry, 701A LGRT
University of Massachusetts
710 North Pleasant Street
Amherst, MA 01003-9336

office: 1502 LGRT Tower A
tel: 413-545-4890 fax: 413-545-4490

lahti@chem.umass.edu

Lahti Research Group

Principal Research Interests

Combining theoretical, synthetic, and physical chemistry to study the electronic properties of molecules, polymers, and materials is the focus of my group. All of our work involves the understanding and electronic properties from a physical organic and materials point of view.

Ab initio, density functional, and semiempirical methods can probe the structure and predicted properties of conjugated molecules and polymers, as well as organic crystals. Understanding spin density distributions in stable radicals helps with designing new soft molecular magnetic materials. Predicting hydrogen bonding and crystal packing can enable the design of crystal “scaffolding.” Also, single molecules with unusual bonding can be computationally studied when experiments yield no definitive answers. For example, matrix isolated intermediates (nitrenes, carbenes) are far easier to identify with computer modeling.
We have devised regiospecific syntheses for polythiophenes and polyphenylene–vinylenes as doped conductors or electroluminescent device ingredients. Regiospecific synthesis can be more difficult than less selective syntheses, but can enhance polymer packing and chromophore planarity. By appropriate substituention, we can fine-tune luminescence wavelengths, processibility, conductivity, and other important polymer properties.

Another major theme of our work is molecule-based magnetism. Organic radicals can be building blocks for magnetic materials, both with and without addition of paramagnetic inorganic metals. We have made organic radicals that show 2-D antiferromagnetism and 1-D ferromagnetic chains that form an antiferromagnetic low temperature phase. Mixtures of similarly shaped organic radicals can assemble by hydrogen-bonding to form bio-inspired dyads between different radicals with complementary interactions, or to form alloys having variable placement of different radicals in a common crystal lattice. Complexes of paramagnetic transition metal ions with coordinating radical ligands have yielded clusters, 1-D chain, 2-D sheet, and 3-D network complexes. Magnetic, thermodynamic, and EPR studies of such systems provide insight about their electronic properties, both at the molecular level and a bulk material level.

“2-(4,5,6,7-Tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1- H-imidazole-3-oxide-1-oxyl, A Hydrogen-Bonded Organic Quasi-1D Ferromagnet,” H. Murata, Y. Miyazaki, A. Inaba, A. Paduan-Filho, V. Bindilatti, N.F. Oliveira, Jr., Z. Delen and P.M. Lahti, J. Am. Chem. Soc.130, 186-194 (2008).

“Single-Molecule Studies of a Model Fluorenone,” M.Y. Odoi, N.I. Hammer, H.P. Rathnayake, P.M. Lahti and M.D. Barnes, ChemPhysChem 8, 1481-1486 (2007).

“Optimizing OLED Efficacy of 2,7-Diconjugated 9,9-Dialkylfluorenes by Variation of Periphery Substitution and Conjugation Length,” H.P. Rathnayake, A. Cirpan, Z. Delen, P.M. Lahti and F.E. Karasz, Adv. Funct. Mater. 17, 115-122 (2007).

“An Organic Radical Solid Solution with Strong Ferromagnetic Exchange,” H. Murata, J.T. Mague, S. Aboaku, N. Yoshioka and P.M. Lahti, Chem. Mater. 19, 4111-4113 (2007).

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