Synthesis, characterization, and redox behavior of new selenium coronands and of copper(I) and copper(II) complexes of selenium coronands

The synthesis and characterization of new selenium coronands and of copper( I) and copper(II) complexes of selenium coronands are reported. Molecular s tructures in the solid state have been determined by X-ray crystallography. The molecular structures of 6,7,13,14-dibenzo-1,5,8,12-tetraselenacy (dibe nzo-14Se4 (1)) and 1,5,9-triselenacyclododecane (12Se3 (2)) adopt conformat ions which maximize the number of possible gauche C-Se-C-C bond torsion ang les. 1: T = 190 K; orthorhombic, space group Pca2(1); fw = 552.19; Z = 4; a = 9.645(3) Angstrom; b = 12.679(6) Angstrom; c 15.332(4) Angstrom; V = 187 4.9 Angstrom(3); R-F = 0.027 for 1732 data (I-o greater than or equal to 2. 5 sigma(I-o)) and 200 variables. 2: T = 190 K; orthorhombic. space group Pn 2(1)a; fw = 363.12; Z = 4; a = 14.943(4) Angstrom, b = 5.638(2) Angstrom; c = 14.229(3) Angstrom, V = 1198.8 Angstrom(3); R-F = 4.026 for 862 data (I- o greater than or equal to 2.5 sigma(I-o)) and 111 variables. The molecular structures of 1,5-diselena-9,13-dithiacyclohexadecane (16Se2S2 (3)) and [C u(16Se2S2)][SO3CF3](2) (4) correspond to those displayed by both of the ana logous tetrathia and tetraselena macrocycles. Compound 3 adopts a [3535] qu adrangular conformation. Compound 4, [Cu(16Se4(OH)2][SO3CF3](2) (5) (where 16Se4(OH)(2) = cis-1,5,9,13-tetraselenacyclohexadecane-3,11-diol), and [Cu( 8Se2(OH))(2)][SO3CF3](2) (6) (where 8Se2(OH) = 1.5-diselenacyclooctan-3-ol) have typical tetragonally distorted octahedral coordination environments o f Cu(II). Compounds 4 and 5 both display a c,t,c configuration of the coron and. Compound 5 has only one hydroxyl group coordinated in an axial positio n, which requires that the corresponding Se-Cu-Se-C-C-C ring be locked into a boat rather than a chair conformation. The hydroxyl groups in 6 occupy t he axial coordination positions. 3: T = 200 K; monoclinic, space group C2/c ; fw = 390.36; Z = 12; a = 24.202(9) Angstrom; b = 18.005(7) Angstrom; c 16 .235(5) Angstrom; beta 138.23(3)degrees; V = 4713 Angstrom(3); R-F = 0.052 for 1881 data (I-o greater than or equal to 2.5 sigma(I-o)) and 172 variabl es. 4: T = 297 K: monoclinic, space group P2(1)/n; fw = 752.03; Z = 2; a = 8.882(2) Angstrom; b = 10.874(2) A; c = 13.360(2) Angstrom; beta = 97.95(2) degrees; V = 1277.9 Angstrom(3); R-F = 0.028 for 1610 data (I-o greater tha n or equal to 2.5 sigma(I-o)) and 176 variables. 5: T = 190 K; monoclinic, space group P2(1)/n; fw = 877.84; Z = 4; a = 8.412(5) Angstrom; b = 20.924( 5) Angstrom; c = 15.021(5) Angstrom; beta = 100.82(4)degrees; V = 2597 Angs trom(3); R-F = 0.059 for 2152 data (I-o greater than or equal to 2.5 sigma( I-o)) and 185 variables. 6: T = 195 K; monoclinic, space group P2(1)/c; fw = 877.84; Z = 2; a = 6.675(2) Angstrom; b = 10.945(2) Angstrom; c = 17.496( 2) Angstrom, beta = 96.76(2)degrees; V = 1307.3 Angstrom(3); R-F = 0.023 fo r 1816 data (I-o greater than or equal to 2.5 sigma(I-o)) and 159 variables . [Cu(16Se2S2)][SO3CF3] (7) and [Cu(16Se4(OH))][SO3CF3] (8) (where 16Se4(OH ) = 1,5,9,13-tetraselenacyclohexadecan-3-ol) are both terrahedral Cu(I) cor onand complexes with typical t,t,t configurations. 7. T = 205 K; triclinic, space group P (1) over bar; fw = 602.97; Z = 2; a = 10.512(3) Angstrom; b = 10.674(2) Angstrom; c = 10.682(3) Angstrom; alpha = 101.47(2)degrees; bet a = 116. 82(2)degrees; gamma = 93.59(2)degrees; V = 1032.3 Angstrom(3); R-F = 0.029 for 2237 data (I-o greater than or equal to 2.5 sigma(I-o)) and 264 variabl es. 8: T = 297 K; monoclinic, space group P2(1)/n; fw = 712.77; Z = 4; a = 13.695(2) Angstrom; b = 11.202(2) Angstrom; c = 14.163(3) Angstrom; beta = 92.35(2)degrees; V = 2170.9 Angstrom(3); R-F = 0.035 for 2086 data (I-o gre ater than or equal to 2.5 sigma(I-o)) and 189 variables. Compounds 5, 6, an d 8 all display hydrogen bonding between hydroxyl groups and the SO3CF3- io ns. Isotropic C-13 and Se-77 chemical shifts have been obtained in the soli d state for 2,3,1,5,9,13-tetraselenacyclohexadecane-3, 11-diol (16Se4(OH)(2 ) (9)), 1,5,9,13-etraselenacyclohexadecan-3-ol (16Se4(OH) (10)), and the di cationic complex 1,5,-(diseleniacyclooctane trifluoromethanesulfonate (8Se2 (SO3CF3)(2) (11)). In addition, the Se-77 chemical shift anisotropies have been determined for 10 and 11. The dicationic compound 11 resonates at lowe r field, reflective of a contribution from the transannular Se-Se bond. The redox behavior of 1-8 has been examined by means of cyclic voltammetry. Re dox behavior of the copper complexes 4, 5, and 6 indicates the presence of two different conformational isomers of the Cu(I) complexes that are oxidiz ed at different potentials, analogous to Rorabacher's copper(II/I) complexe s that follow a dual-pathway square-scheme mechanism. The quasi-reversible cyclic voltammograms observed for the Cu(II) complexes of selenium coronand s reflect the configurational changes between Cu(II) complexes (octahedral or tetragonal configurations) and Cu(T) complexes (tetrahedral configuratio ns) and indicate that the configurational changes are slower than the elect ron transfers to the electrode.