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

✍ Scribed by M. J. Chen; J. W. Rathke

• Book ID: 102399768
• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 162 KB
• Volume: 05
• Category: Article
• ISSN: 1088-4246
• DOI: 10.1002/jpp.359

✦ Synopsis

The ^1^ H 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 × 10^2^, 5.7 × 10^2^, and 1.0 × 10^3^ M ^-1^, respectively. In chloroform, aggregation of the complex occurs at ~0.3 mM, reflecting the lower solvating power of chloroform for this complex. The ^1^ H 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 ^1^ H NMR spectra of the major isomer, 2a, suggest that it is the 45 °-staggered cofacial dimer, a dimer with a D~4 d~ symmetry. The ^1^ H NMR spectra of the minor isomer, 2b, suggest that it is a slipped cofacial dimer with a C~2 h~ symmetry, which is formed by slipping a ( RPc ) Rh plane of the eclipsed dimer (a D~4 h~ 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.