Quantum Mechanical and Experimental Validation that Cyclobis(paraquat-p-phenylene) Forms a 1:1 Inclusion Complex with Tetrathiafulvalene
| Autor: | Amy A. Sarjeant, Marco Frasconi, J. Fraser Stoddart, Nema Hafezi, Sanjeev K. Dey, Albert C. Fahrenbach, Charlotte L. Stern, Wei Guang Liu, Karel J. Hartlieb, William A. Goddard, Anthea K. Blackburn |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Steric effects
Rotaxane 010405 organic chemistry Stereochemistry donor-acceptor systems Organic Chemistry Intermolecular force Chemistry (all) Solvation General Chemistry 010402 general chemistry DFT calculations 01 natural sciences Catalysis 0104 chemical sciences chemistry.chemical_compound Crystallography rotaxanes chemistry tetrathiafulvalene Molecule Dumbbell Cyclobis(paraquat-p-phenylene) Tetrathiafulvalene |
| Popis: | The promiscuous encapsulation of π-electron-rich guests by the π-electron-deficient host, cyclobis(paraquat-p-phenylene) (CBPQT^(4+)), involves the formation of 1:1 inclusion complexes. One of the most intensely investigated charge-transfer (CT) bands, assumed to result from inclusion of a guest molecule inside the cavity of CBPQT^(4+), is an emerald-green band associated with the complexation of tetrathiafulvalene (TTF) and its derivatives. This interpretation was called into question recently in this journal based on theoretical gas-phase calculations that reinterpreted this CT band in terms of an intermolecular side-on interaction of TTF with one of the bipyridinium (BIPY^(2+)) units of CBPQT^(4+), rather than the encapsulation of TTF inside the cavity of CBPQT^(4+). We carried out DFT calculations, including solvation, that reveal conclusively that the CT band emerging upon mixing TTF with CBPQT^(4+) arises from the formation of a 1:1 inclusion complex. In support of this conclusion, we have performed additional experiments on a [2]rotaxane in which a TTF unit, located in the middle of its short dumbbell, is prevented sterically from interacting with either one of the two BIPY^(2+) units of a CBPQT^(4+) ring residing on a separate [2]rotaxane in a side-on fashion. This [2]rotaxane has similar UV/Vis and ^1H NMR spectroscopic properties with those of 1:1 inclusion complexes of TTF and its derivatives with CBPQT^(4+). The [2]rotaxane exists as an equimolar mixture of cis- and trans-isomers associated with the disubstituted TTF unit in its dumbbell component. Solid-state structures were obtained for both isomers, validating the conclusion that the TTF unit, which gives rise to the CT band, resides inside CBPQT^(4+). |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|