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Inhibition of Ligand Binding Ability of Three Porphyrins by an Organic Effector
Author(s) -
Nishimura Tomoaki,
Sasaki Yoshito,
Tachi Yoshimitsu,
Suzuki Shuichi,
Okada Keiji,
Kozaki Masatoshi
Publication year - 2020
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201901711
Subject(s) - chemistry , ligand (biochemistry) , allosteric regulation , supramolecular chemistry , stereochemistry , zinc , hydrogen bond , molecule , crystallography , tetraphenylporphyrin , titration , receptor , porphyrin , photochemistry , crystal structure , inorganic chemistry , organic chemistry , biochemistry
A stimulus‐responsive receptor 1 was designed and prepared to control the ligand‐binding ability of three active sites, two zinc tetraphenylporphyrin units (P1) and one zinc diethynyldiphenylporphyrin unit (P2), with one effector molecule 2 . Bulky hexarylbenzene units were incorporated as shielding panels in the middle of the flexible side arms of 1 . Spectroscopic titrations indicated that a stable supramolecular complex 1 ⋅ 2 ( K 1 ⋅ 2 =6.7×10 6 m −1 ) was produced by the cooperative formation of multiple hydrogen and coordination bonds. As a result, the binding of a ligand to P1 was inhibited by 2 in a competitive manner. Additionally, the formation of 1 ⋅ 2 brought about conformational restriction of the side arms to cover both faces of P2 with the shielding panels. The binding constant of 4‐phenylpyridine with P2 in 1 ⋅ 2 decreased to 8.9 % of that in 1 . Namely, the ligand‐binding ability of P2 was inhibited according to an allosteric mechanism.