Molecular gears: Structures of (9,10-triptyceno) crown ethers

The incorporation of 9,10-triptycene unit in a crown ether is examined from a structural perspective. Insertion of a triptycene group into 18-crown-6 stretches the crown into an ellipse, as seen in structures presented here o f 9,10-triptyceno-22-crown-6 and its thallium complex. Symmetric addition o f two triptycene groups into 18-crown-6 results in the sterically congested bis(9,10-triptyceno)-26-crown-6, whose crown cavity is filled with the pi- clouds of two arene groups. The larger bis(9,10-triptyceno)-32-crown-8 is m ore sterically relaxed. The structures of these bis(triptyceno)crown ether molecules are the first with two triptycene groups simultaneously linked th rough their 9 and 10 positions, thereby forming a simple molecular gearing mechanism. The compound 9,10-triptyceno-22-crown-6 (1) crystallizes in the orthorhombic space group Pbca with a = 10.7962(7), b = 15.826(3), c = 31.14 7(5) Angstrom, V = 5321.8(12) Angstrom(3), and Z = 8; its complex with TlNO 3 (Tl-1) crystallizes in the monoclinic space group P2(1)/c with a = 8.1884 (14), b = 19.552(2), c = 20.575(4) Angstrom, beta = 97.062(8)degrees, V = 3 269.2(9) Angstrom(3), and Z = 4; bis(9,10-triptyceno)-26-crown-6 (2) crysta llizes in the triclinic space group <P(1)over bar> with a = 8.6488(11), b = 10.7718(12), c = 12.3324(12) Angstrom, alpha = 111.58(1), beta = 100.55(1) , gamma = 106.43(1)degrees, V = 970.3(5) Angstrom(3), and Z = 1; and bis(9, 10-triptyceno)-32-crown-8 (3) crystallizes in the orthorhombic space group Pna2(1) with a = 20.186(3), b = 8.558(2), c = 25.623(2) Angstrom, V = 4426. 2(14) Angstrom(3), and Z = 4.