The Library
Potentiometric titrations and nickel(II) complexes of four topologically constrained tetraazamacrocycles
Tools
Tools
Tools
UNSPECIFIED (2001) Potentiometric titrations and nickel(II) complexes of four topologically constrained tetraazamacrocycles. SUPRAMOLECULAR CHEMISTRY, 13 (2). pp. 261-276. ISSN 1061-0278
Full text not available from this repository.Abstract
The novel high spin Ni2+ complexes of the topologically constrained tetraazamacrocycles (1-4) [4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (1); 4,10-dimethyl-1,4,7,10-tetraazabicyclo[6.5.2]pentadecane (2); 4,10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane (3); racemic-4,5,7,7,11,12,14, 14-octamethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (4)] show striking properties. Potentiometric titrations of the ligands 2 and 4 revealed them to be proton sponges, as reported earlier for 1 [1]. Ligand 3 is less basic, losing its last proton with a pK = 11.3(2). Despite high proton affinities, complexation reactions in the absence of protons successfully yielded Ni2+ complexes in all cases. The X-ray crystal structures of Ni(1)(acac)(+), Ni(3)(acac)+ and Ni(1)(OH2)(2)(2+) demonstrate that the ligands 2 enforce a distorted octahedral geometry on Ni2+ with two cis sites occupied by other ligands. Magnetic measurements and electronic spectroscopy on the corresponding Ni(L)Cl-2. (L = 1 - 3) complexes reveal that all are high spin and six-coordinate with typical magnetic moments. In contrast, [Ni(4)Cl+] is five-coordinate with a slightly higher magnetic moment and its own characteristic electronic spectrum. The extra methyl groups on ligand 4 define a shallow cavity, sterically allowing only one chloride ligand to bind to the nickel(II) ion.
| Item Type: | Journal Article |
|---|---|
| Subjects: | Q Science > QD Chemistry |
| Journal or Publication Title: | SUPRAMOLECULAR CHEMISTRY |
| Publisher: | GORDON BREACH PUBLISHING, TAYLOR & FRANCIS GROUP |
| ISSN: | 1061-0278 |
| Date: | 2001 |
| Volume: | 13 |
| Number: | 2 |
| Number of Pages: | 16 |
| Page Range: | pp. 261-276 |
| Publication Status: | Published |
| URI: | http://wrap.warwick.ac.uk/id/eprint/11902 |
Data sourced from Thomson Reuters' Web of Knowledge
Actions (login required)
 |
View Item |
