Characterization of the Structural and Electronic Properties of Spin-Coupled Dinuclear Copper(II) Centers by Proton NMR Spectroscopy

Authors

Julie M. Brink, Utah State University
Rachel A. Rose, Utah State University
Richard C. Holz, Marquette UniversityFollow

Document Type

Article

Publication Date

1996

Source Publication

Inorganic Chemistry

Source ISSN

0020-1669

Abstract

The ¹H NMR spectra of a series of well-characterized μ-phenoxo and μ-alkoxo spin-coupled dicopper(II) complexes have been investigated. The complexes studied were [Cu₂(BPMP)(OH)]²⁺ (1) (BPMP = 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol), [Cu₂(CH₃HXTA)(OH)]^2- (2) (CH₃HXTA = N,N ‘-(2-hydroxy-5-methyl-1,3-xylylene)bis(N-carboxymethylglycine), [Cu₂(m-XYL)(OH)]²⁺ (3) (m-XYL = 2,6-bis[[bis(2-pyridylethyl)amino]methyl]phenol), and [Cu₂(TBHP)(OAc)]²⁺ (4) (TBHP = N,N,N ‘,N  ‘-tetrakis[(2-benzimidazolyl)methyl]-2-hydroxy-1,3-diaminopropane). The magnetic interactions of these complexes range from strongly antiferromagnetically to weakly ferromagnetically coupled. Both one- and two-dimensional (COSY) ¹H NMR methods were used to facilitate the assignment of the hyperfine shifted ¹H NMR signals of each complex. COSY experiments provide clear cross signals for resonances ¹H NMR signals and have verified that the solid state structures exist in solution for each system studied. Assuming a paramagnetic dipolar relaxation mechanism, the crystallographically determined Cu−H distance (r) is proportional to T₁^1/6. All calculated Cu−H distances for 1−4 are within ca. 20% of the Cu−H distances derived from X-ray crystallography. These data indicate that a paramagnetic dipolar relaxation mechanism is the dominant proton relaxation pathway for spin-coupled dicopper(II) centers. Our results indicate that ¹H NMR spectroscopy is an excellent tool with which to probe the solution structures of spin-coupled dicopper(II) centers in model complexes as well as biological systems.

Comments

Accepted version. Inorganic Chemistry, Vol. 35, No. 10 (1996): 2878-2885. DOI. © 1996 American Chemical Society Publications. Used with permission.

Richard Holz was affiliated with the Utah State University at the time of publication.

Recommended Citation

Brink, Julie M.; Rose, Rachel A.; and Holz, Richard C., "Characterization of the Structural and Electronic Properties of Spin-Coupled Dinuclear Copper(II) Centers by Proton NMR Spectroscopy" (1996). Chemistry Faculty Research and Publications. 300.
https://epublications.marquette.edu/chem_fac/300