Field-induced π-polarization in barrelene derivatives: a computational study based on structural variation
| Autor: | Fabio Ramondo, Aldo Domenicano, Anna Rita Campanelli |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Substituted barrelenes
Field-induced π-polarization Double bond Stereochemistry Substituent Dipole moments Electronegativity effect Field effect Structural variation Substituted bicyclo[2.2.2]octanes Condensed Matter Physics Physical and Theoretical Chemistry 010402 general chemistry 01 natural sciences Electronegativity chemistry.chemical_compound 0103 physical sciences Phenyl group Molecule Octane chemistry.chemical_classification 010304 chemical physics Barrelene 0104 chemical sciences Crystallography dipole moments electronegativity effect field effect field-induced π-polarization structural variation substituted barrelenes substituted bicyclo[2.2.2]octanes Molecular geometry chemistry |
| Zdroj: | Structural Chemistry. 28:617-624 |
| ISSN: | 1572-9001 1040-0400 |
| Popis: | Barrelene, H–C(CH=CH)3C–H, is an unsaturated polycyclic hydrocarbon containing three isolated double bonds in a non-planar arrangement. We have studied the transmission of field effects through the barrelene framework by analyzing the small structural changes occurring in the phenyl group of many Ph–C(CH=CH)3C–X molecules, where X is a variable substituent. Molecular geometries have been determined by quantum chemical calculations at the HF/6-31G* and B3LYP/6-311++G** levels of theory. Comparison with the results obtained for the corresponding saturated molecules, the bicyclo[2.2.2]octane derivatives Ph–C(CH2–CH2)3C–X, reveals a small, but significant, field-induced π-polarization of the barrelene cage, especially when the remote substituent is a charged group. Additional evidence of π-polarization is obtained by comparing the electric dipole moments of the two sets of uncharged molecules. The structural variation of the barrelene cage caused by the variable substituent in Ph–C(CH=CH)3C–X molecules has also been investigated. It is much larger than that of the phenyl group and depends primarily on the electronegativity of the substituent. Particularly pronounced is the concerted variation of the non-bonded distance between the bridgehead carbons of the cage, r(C···C) 1 BARR , and the average of the three C–C–C angles at the cage carbon bonded to the variable substituent, α 1 BARR . A scattergram of r(C···C) 1 BARR versus the corresponding parameter for bicyclo[2.2.2]octane derivatives, r(C···C) 1 BCO , shows that the variation of r(C···C) 1 BARR becomes gradually less pronounced than that of r(C···C) 1 BCO as the electronegativity of the substituent increases. |
| Databáze: | OpenAIRE |
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