TY - JOUR
T1 - Novel Aromatic Cations and Anions
T2 - Aromaticity-Structure Relationships
AU - Rabinovitz, Mordecai
AU - Willner, Itamar
PY - 1980
Y1 - 1980
N2 - In aromatic polycyclic systems both the local contribution of the components and the peripheral π-delocalization influence the net aromatic nature of the system. Polycyclic conjugated systems are classified according to the number of π-electrons involved in each ring. A (4n. + 2)π + (4n2 + 2)π fusion results in a (4n + 2)π periphery. Indeed, these systems have aromatic character. However, steric effects (e.g. peri H-H interactions and biphenyl backbone) influence the gradual formation of the aromatic ions and direct their stereochemistry. A (4nl + 2)π + 4n2π fusion results in an antiaromatic 4nπ periphery. The fusion of a cyclo-pentadienyl anion to a planar COT component in a polycycle shows paratropic character. Oxidation of a polycyclic molecule which includes a planar COT component yields an aromatic system which includes a COT++’ moiety. The fusion of 4nlπ + 4n2π systems represents an aromatic (4n + 2)π periphery, while the components are antiarcmatic. The preparation of benzannelated pentalene dications shows that they exhibit diatropicity and that the peripheral (4n + 2)π delocalization dominates. The two electron oxidation and reduction of dibenzopentalenes to the respective aromatic dications and dianions show that 4nπ conjugated polycycles behave similarly to the corresponding monocycles in attaining aromatic character.
AB - In aromatic polycyclic systems both the local contribution of the components and the peripheral π-delocalization influence the net aromatic nature of the system. Polycyclic conjugated systems are classified according to the number of π-electrons involved in each ring. A (4n. + 2)π + (4n2 + 2)π fusion results in a (4n + 2)π periphery. Indeed, these systems have aromatic character. However, steric effects (e.g. peri H-H interactions and biphenyl backbone) influence the gradual formation of the aromatic ions and direct their stereochemistry. A (4nl + 2)π + 4n2π fusion results in an antiaromatic 4nπ periphery. The fusion of a cyclo-pentadienyl anion to a planar COT component in a polycycle shows paratropic character. Oxidation of a polycyclic molecule which includes a planar COT component yields an aromatic system which includes a COT++’ moiety. The fusion of 4nlπ + 4n2π systems represents an aromatic (4n + 2)π periphery, while the components are antiarcmatic. The preparation of benzannelated pentalene dications shows that they exhibit diatropicity and that the peripheral (4n + 2)π delocalization dominates. The two electron oxidation and reduction of dibenzopentalenes to the respective aromatic dications and dianions show that 4nπ conjugated polycycles behave similarly to the corresponding monocycles in attaining aromatic character.
UR - http://www.scopus.com/inward/record.url?scp=82255193518&partnerID=8YFLogxK
U2 - 10.1351/pac198052061575
DO - 10.1351/pac198052061575
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AN - SCOPUS:82255193518
SN - 0033-4545
VL - 52
SP - 1575
EP - 1585
JO - Pure and Applied Chemistry
JF - Pure and Applied Chemistry
IS - 6
ER -