Premium
Efficient Host‐Guest Complexation of a Bisporphyrin Host with Electron Deficient Guests: Synthesis, Structure, and Photoinduced Electron Transfer
Author(s) -
Mondal Pritam,
Rath Sankar Prasad
Publication year - 2016
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.201500014
Subject(s) - chemistry , electron transfer , acceptor , photoinduced electron transfer , electron donor , photochemistry , electron acceptor , crystallography , excited state , molecule , host–guest chemistry , stereochemistry , crystal structure , catalysis , organic chemistry , supramolecular chemistry , nuclear physics , condensed matter physics , physics
The encapsulation of 1,8‐naphthalic anhydride (NAN), 9‐dicyanomethylenefluorene (9‐DCF), acenaphthenequinone (ANQ), and 4‐chloro‐7‐nitrobenzofurazan (NBD‐Cl) by diethylpyrrole‐bridged bisporphyrin (H 4 DEP) and its dizinc(II) analogue (Zn 2 DEP) are employed to investigate the structural and spectroscopic changes within the bisporphyrin cavity upon substrate binding. Synthesis and X‐ray structures of all four encapsulated host‐guest complexes (H 4 DEP⋅NAN, H 4 DEP⋅9‐DCF, Zn 2 DEP⋅ANQ, and Zn 2 DEP⋅NBD‐Cl) are reported here. The binding constant calculations show strong 1 : 1 binding between the hosts (H 4 DEP and Zn 2 DEP) and the guests (NAN/9‐DCF/ANQ/NBD‐Cl). 1 H‐NMR spectra also support the retention of the host‐guest assemblies in solution. Negative and positive shifts of the reduction and oxidation potentials, respectively, indicate that it is difficult to reduce/oxidize the encapsulated complexes. The emission intensities of the bisporphyrins (H 4 DEP and Zn 2 DEP) are substantially quenched in all the complexes, owing to photoinduced electron transfer from the excited state of the bisporphyrins to guest molecules. All the experimental evidence is further substantiated by DFT calculations. Such an efficient electron transfer is only possible when the donor and the acceptor moieties are in close propinquity to each other, which eventually lowers the reorganization energy.