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Quantitative Analysis of Self‐Assembly Process of a Pd 2 L 4 Cage Consisting of Rigid Ditopic Ligands
Author(s) -
Kai Shumpei,
MartíCentelles Vicente,
Sakuma Yui,
Mashiko Takako,
Kojima Tatsuo,
Nagashima Umpei,
Tachikawa Masanori,
Lusby Paul J.,
Hiraoka Shuichi
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704285
Subject(s) - chemistry , ligand (biochemistry) , intramolecular force , self assembly , crystallography , acetylene , benzene , ring (chemistry) , trigonal bipyramidal molecular geometry , cage , metal , stereochemistry , crystal structure , organic chemistry , combinatorics , biochemistry , receptor , mathematics
The self‐assembly process of a Pd 2 L 4 cage complex consisting of rigid ditopic ligands, in which two 3‐pyridyl groups are connected to a benzene ring through acetylene bonds and Pd II ions was revealed by a recently developed quantitative analysis of self‐assembly process (QASAP), with which the self‐assembly process of coordination assemblies can be investigated by monitoring the evolution with time of the average composition of all the intermediates. QASAP revealed that the rate‐determining steps of the cage formation are the intramolecular ligand exchanges in the final stage of the self‐assembly: [Pd 2 L 4 Py* 2 ] 4+ →[Pd 2 L 4 Py* 1 ] 4+ +Py* and [Pd 2 L 4 Py* 1 ] 4+ →[Pd 2 L 4 ] 4+ +Py* (Py*: 3‐chloropyridine, which was used as a leaving ligand on the metal source). The energy barriers for the two reactions were determined to be 22.3 and 21.9 kcal mol −1 , respectively. DFT calculations of the transition‐state (TS) structures for the two steps indicated that the distortion of the trigonal‐bipyramidal Pd II center at the TS geometries increases the activation free energy of the two steps.