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Dimeric aggregates of five-coordinated methyl(phthalocyaninato)Rh(III): ¹H NMR evidence for staggered and slipped cofacial dimers

Chemical Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA

Corresponding author, Chemical Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.

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J. W. RATHKE

Chemical Technology Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA

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https://doi.org/10.1002/jpp.359Cited by:12 (Source: Crossref)

Abstract

The ¹H NMR spectra of the five-coordinated rhodium phthalocyanine complex Me(RPc)Rh(III) (1, RPc = dianion of 1,4,8,11,15,18,22,25-octa-n-pentylphthalocyanine) in toluene indicate that it exists as a discrete monomer at low concentrations. The complex forms a dimer aggregate reversibly in the concentration range of 2.6–10.2 mM at -90 < T < 22 °C. The dimerization constants at -60, -80, and -90 °C are 2.0 × 10², 5.7 × 10², and 1.0 × 10³M^-1, respectively. In chloroform, aggregation of the complex occurs at ~0.3 mM, reflecting the lower solvating power of chloroform for this complex. The ¹H NMR spectra of the chloroform solutions indicate that at concentrations greater than 1.0 mM, two discrete dimers in the ratio of 87:13 are reversibly formed. The ¹H NMR spectra of the major isomer, 2a, suggest that it is the 45 °-staggered cofacial dimer, a dimer with a D_4d symmetry. The ¹H NMR spectra of the minor isomer, 2b, suggest that it is a slipped cofacial dimer with a C_2h symmetry, which is formed by slipping a (RPc)Rh plane of the eclipsed dimer (a D_4h dimer) along a line connecting two opposing meso nitrogens of (RPc)Rh. Interestingly, the solution conformation of 2b is similar to that of the basic stacking unit found in the crystal structure of 1.

This article is a U.S. Government work and is in the public domain in the U.S.A.

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