Journal
INORGANICA CHIMICA ACTA
Volume 372, Issue 1, Pages 62-70Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.ica.2011.01.101
Keywords
Zn-bisporphyrin; Molecular switching; Tweezer complex; Binding constant; Structure elucidation
Categories
Funding
- Department of Science and Technology, Government of India
- CSIR, New Delhi
Ask authors/readers for more resources
Stepwise addition of 1,2-diaminobenzene to a Zn-1,2-bis(meso-octaethylporphyrinyl)ethane produces both tweezer and anti-form of the complex depending on the concentration of the axial ligand which exhibit two major equilibrium steps (with two step-wise binding constants): first, guest ligation leading to the formation of 1:1 host-guest tweezer structure (K-1) and, second, guest molecule ligation (K-2) forming 1:2 host-guest anti species and the corresponding binding constants are 1.82 x 10(3) M-1 and 1.34 x 10(2) M-1, respectively. However, when guest like 1,4-diaminobenzene and 4-CN-pyridine are used, the ligand geometry prevents its entry into interporphyrin cavity to form a tweezer structure, thus producing only the 1:2 anti complex. Single crystal X-ray structures of both tweezer and anti form produced in a single Zn-bisporphyrin are reported here for the first time. The nonbonding Zn center dot center dot center dot Zn distance within a molecule is 5.55 and 10.01 angstrom in tweezer and anti form, respectively. Although the average Zn-N (por) distances are comparable for both the forms, the Zn-N (1,2-diaminobenzene/4-CN-pyridine) distances and the displacement of Zn from the mean porphyrin planes are larger in tweezer compared to anti conformation. (C) 2011 Elsevier B. V. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available