Macro rings. XL. Transannular interactions in the tetracyanoethylene complexes of [3.3]paracyclophane and derivatives

Abstract

Equilibrium constants for 1:1 -salt formation between tetracyanoethylene and [3.3]-, [3.4]-, [2.2]-, [1.9]-, [9]-, [4.4]-, and [6.6]paracyclophane were found to decrease in value in the order listed, the values being higher than that for the open-chain model compound, 1,3-bis(4-ethylphenyl)propane. A rough linear correlation between the equilibrium constants and the position of the \mix of the long-wavelength charge-transfer band in the visible spectrum of the -salts has been observed for these and four monosubstituted [2.2]paracyclophanes. An exception to the correlation was the -salt of [4.4]paracyclophane. The positions of max values of the long-wavelength chargetransfer band of the -salts of 13 substituted [3.3]paracyclophanes were determined. Possible correlations between A£t's (differences in electronic transition energies between the 5-substituted [3.3]paracyclophanes and [3.3]paracyclophane itself) and substituent constants were examined. A rough linear correlation was observed between AEt values and ," constants for the electron-withdrawing substituents. The nonsubstituted ring was the more basic of the two, and was probably the main site of salt formation. This correlation demonstrates the presence of transannular electronic effects in the [3.3]paracyclophane system. Comparison of the slope of the plot for the [3.3]paracyclophane derivatives with the formerly determined slope of the plot for the [2.2]paracyclophane derivatives demonstrated the transannular effects in the latter system to be greater. An even poorer linear correlation was observed between AEt of -salts of [3.3]paracyclophane substituted with electron-providing groups and + (r = 0.25) values. From its AEt value the acetamido substituent appeared to function as a moderately strong electron-withdrawing group when attached to [3.3]paracyclophane, whereas its " value indicates that the group should be a weak electron donor. This abnormal behavior was also observed for 5-acetamido[3.4]paracyclophane, but not for 4-acetamido[2.2]paracyclophane. The 1:1 tetracyanoethylene-[3.3]paracyclophane salt was prepared in a crystalline form and analyzed.The formation of stable --salts between tetra-cyanoethylene2 3(TCNE) and the [m.njparacyclo-phanes3a provided a simple means of investigating the change in the -base strength of the aromatic hydrocarbons with changes in values of m and n,3a and with changes in substituents on the aromatic nucleus of [2.2]paracyclophane.3b The relative basicities of the (CH2)" tetracyanoethylene [m. nlparacyclophane -acid base (1) The authors wish to thank the National Science Foundation for a grant used in support of this research. M. S. also wishes to thank the National Science Foundation for a National Science Foundation Predoctoral Fellowship, 1965Fellowship, -1969 (2) T.

Protonation studies on isomeric tetrafluoro‐2,11‐dithia[3·3]cyclophanes, tetrafluoro[2·2]metaparacyclophane and their corresponding non‐fluorinated analogs. Comparison with fluorinated and non‐fluorinated[2·2]cyclophanes: A stable ion and semi‐empirical (AM1, PM3) investigation

“…The phenyl rings in bo!h of the neutral dithiacyclophanes are within 3 of planarity. However, examination of the optimized geometry of the dithia[3.3]paracyclophane 6 and its disulfonium ion 6-H$+ (Table 3) reveals that diprotonation increases t h: strain by spreading the C-S-S angles (6) by 6.2 . This in turn increases the deviation of the benzene rings from planarity by 3.4 , despite the fact that the CS bonds also increase in length by 0.028A, and the ends of the opposing rings move further apart by 0.30 A. Energies and charges The A& value for @so (C-3) protonation of [2.2] purucyclophane, 3, is calculated to be 174.6 kcalmol-I (181.0 kcalmol-' for PM3) (1 kcal= 4.184 kJ), whereas that of [2*2]metupurucyclophane, 4, is 181.6, 171-9 and 168-3 for protonation on C-11, C-12 and C-3, respectively (Figure 9).…”

Theoretical study of substituent effects on the geometry and strain enthalpy in [2,2]paracyclophanes

“…Introduction of a substituent to the [2,2]paracyclophane has direct influence on the electronic space structure between the aromatic moieties. Sheehan and Cram (Sheehan and Cram, 1969) reported experimental studies of the influence of several substituents at one aromatic ring on the other unsubstituted ring.…”

Charge-transfer interaction of 4,13-diamino[2.2]paracyclophane with π-acceptors

“…[1][2][3] In recent years we reported on the synthesis of some interesting new heterocyclic systems by CT-complexation between simple heterocycles as electron donors and various π-acceptors. [4][5][6][7][8][9][10][11][12][13] In 1993 Mourad et al 14 Recently, we have furthermore succeeded to construct a variety of poorly investigated types of heterocyclic compounds such as pleiadenes and perimidines, by the reaction of 1,8-diaminonaphthalene with selected π-acceptors.…”