Stephen M. Holmes

Research Interests

Magnetic Materials. 
Understanding the physical origins of single-molecule magnetic behavior in a series of structurally related cyanometalate clusters is an active area of study. Cyanometalatesare excellent building blocks for constructing molecule-based clusters because cyanides generally form linear M(m-CN)M´ linkages between two metal centers, stabilize a variety of transition metal centers and oxidation states, and efficiently communicate spin density information. Furthermore the sign and magnitude of the local exchange interactions can be controlled via substitution and predicted using simple orbital symmetry arguments. We have developed a synthetic methodology for preparing several well-defined clusters containing a variety of tricyanide complexes (building blocks). The building blocks exhibit significant orbital contributions to their magnetic moments, apparently a necessary feature for the observation of slow magnetic relaxation. Current efforts are focused on how late transition metal centers alter the magnetic (and optical) properties of structurally related clusters.

Photoresponsive Materials.
Compounds that change their optical, magnetic, and electrical properties as a function of external stimuli is an exciting area of study in materials science. We recently reported that two polynuclear cyanometalate complexes exhibit reversible changes their optical and magnetic properties with temperature (up to 250 K) and light. If this is a general phenomenon, then substitution of the metal ions and ligands present may extend the operable switching temperatures of these materials above 300 K. Current efforts are directed at understanding the factors necessary for tuning thephotoresponsive behavior in these clusters and one-dimensional networks.

Molecule-Based Devices.
The increasing demand for higher information density and circuit miniaturization is rapidly approaching the limits of device scaling technologies, with potential cost and performance limits being realized within a decade. An overarching goal of molecule-based electronics is to insert easily modified molecules that function as switching elements into electronic devices, in principle allowing for information storage at the molecular level. Key challenges of this collaborative research effort are to (1) fabricate nm-scale electrode gaps that correspond to molecular length scales and (2) engineer tunable molecules for study. Recent measurements suggest that we have successfully integrated a series of magnetic clusters into electrical junctions. Future efforts will investigate how the clusters and metal ions present tune the electrical transport behavior of assembled devices.

Selected Publications

″Structure-Property Studies of a Four Coordinate Niobium(IV) Amide″, F. Shen, R. Jagan, and S. M. Holmes, Polyhedron 2024, in press.

″Cyanide-Bridged Rope-like Chains Based on Trigonal-Bipyramidal [Fe₂Cu₃] Subunits″, J. Yang, M-L. You, S. Liu, Y-F Deng, X-Y. Chang, S. M. Holmes and Y-Z. Zhang, Inorg. Chem., 2023, 62, 17530

″Thermo- and photo-induced electron transfer in a series of [Fe₂Co₂] capsules,″ L. Meng, Yi-F. Deng, S. M. Holmes, and Y-Z. Zhang, Dalton Trans., 2022, 52, 1616.

"Structure-property studies of a new {Fe^III₂Mn^II} comple,x" N. P. Rath and S. M. Holmes, Polyhedron 2021, 206, 115324.

 ″Structure-​property studies of a new one-​dimensional Fe(III)​/Mn(II) chain,″ Y-Z Zhang, N. P. Rath, J. M. Cain, M. W. Meisel and S. M. Holmes, Polyhedron, 2020, 179, 114376

″Synthesis and characterization of first row transition metal p-toluenesulfonate complexes and chains,″ P. J. Ferko, J. R. Withers, H. Nguyen, C. Allison, J. Ema, T. Ema, N. P. Rath, Y-Z Zhang and S. M. Holmes, Polyhedron, 2017, 123, 344.

″Simultaneous Introduction of Redox and Coordination Chemistry Concepts in a Single Laboratory Experiment,″ P. J. Ferko, J. R. Withers, H. Nguyen, J. Ema, T. Ema,  C. Allison, C. Dornhoefer,  N. P. Rath and S. M. Holmes, J. CHEM. EDUC. 2017, 94, 95

″Structure-Property Relationships in Tricyanoferrate(III) Building Blocks and Trinuclear Cyanide-Bridged Complexes″ Y. Zhang, U. P. Malik, B. Quiggins, H. Nguyen, C. C. Beedle, A. E. Kovalev, R. Clerac, S. Hill , B. J. Bythell, Benjamin and S. M. Holmes, Eur. J. Inorg. Chem. 2016, 15, 2432.

″Spin-state switches in molecular materials chemistry,″ S. Hayami, S. M. Holmes and M. A. Halcrow,″ J. Mater. Chem. C, 2015, 3, 7775. 

″Thermochromic and Photoresponsive Cyanometalate Fe/Co Squares: Towards Control of the Electron Transfer Temperature,″ Y. Z. Zhang, P. Ferko, D. Siretanu, R. Ababei, N. P. Rath, M. J. Shaw, R. Clérac, C. Mathonière, and S. M. Holmes, J. Am. Chem. Soc. 2014, 136, 16854.

"Pyrazolylborate cyanometallate single-molecule magnets," P. J. Ferko and S. M. Holmes, Curr. Inorg. Chem. 2013, 3, 172.

"A cyanide-bridged trinuclear {Fe^III₂Ni^II} complex decorated with organic radicals," Y-Z. Zhang, D-F. Li, R. Clerac and S. M. Holmes, Polyhedron 2013, 60, 110.

 "EPR studies of a cyano-bridged {Fe₂^IIINi^II) coordination complex and its corresponding FEIII mononuclear building block,"  C. C. Beedle, Y-Z.  Zhang, S. M. Holmes and S. Hill, Polyhedron 2013, 59, 48.

"Structure-property trends in cyano-bridged tetranuclear Fe^III/Ni^II single-molecule magnets," Y-Z. Zhang, U. P. Malik, R. Clerac, N. P. Rath and S. M. Holmes, Polyhedron, 2013, 52, 115.

"Synthesis, Structures, and Magnetic Properties of a Novel mer-[(bbp)Fe^III(CN)₃]^2- Building Block (bbp:bis(2-benzimidazolyl)pyridine dianion) and Its Related Heterobimetallic Fe(III)-Ni(II) Complexes," A. Panja, P. Giuionneau, I-R Jeon, S. M. Holmes, R. Clerac and C. Mathoniere, Inorg. Chem. 2012, 51, 12350