CONSTRUCTION OF STRUCTURAL PROTOTYPES FOR CATION-RADICAL SALTS OF A LARGE, SPHERICAL PI-DONOR MOLECULE BY MONITORING THE CHARGE OF ISOSTERIC ANIONS - H2CL2-SUBSET-OF-CRYPTOPHANE-E-CENTER-DOT-)(CH3CN)2 (ANTIFLUORITE) AND UBSET-OF-CRYPTOPHANE-E-CENTER-DOT+)RE6S5CL9-(CSCL) AND THEIR ESR PROPERTIES()2MO6BR14(2)

There is currently intense interest in molecular-level approaches to s upramolecular ordered materials [1], particularly in the design and pr ediction of electroactive molecular assemblies with a precise crystall ine organization. The conducting, magnetic or optical properties of th ese assemblies often critically depend on their type and degree or ord er [2]. Large, cage-like spherical molecules in which several redox fu nctionalities are held together in a non-planar configuration were rec ently used in the construction of cation radical salts with three-dime nsional character [3]. Thus, when a cryptophane E, 1 of ca. 12.7 angst rom in diameter is associated with smaller inorganic monoanions of ca 5.0 to 5.6 angstrom in diameter, such as X- = BF4-, PF6-, ClO4- or ReO 4-, the latter are found to fit into the octahedral sites of a cubic f ace-centered array of bulky three-dimensional organic radicals 1.+. Ea ch organic radical also incorporates a chloroform molecule, which yiel ds a unique series of molecular salts that almost have the rock-salt s tructure, (CHCl3 E.+)X-. This is in agreement with an r(X-)/r1.+ radiu s ratio of 0.45 and is consistent with 6-coordinate anions. It is inte resting to observe that a rhombohedral lattice (alpha(R) congruent-to 61-degrees) is obtained throughout the series with one oxidized cage E per unit-cell [3] (for the rock-salt structure alpha(R) = 60-degrees) . The construction of such cation radical salts using the cryptophane E pi-donor molecule and hexanuclear all-inorganic cluster anions of si milar size and shape but different charges, is the subject of this pap er. Two spherical inorganic molecular anions were used with 1.+, namel y the hexanuclear molybdenum bromide cluster dianion, Mo6Br142- (2) (d iameter 10.30 angstrom; volume 575 angstrom3 [4]) and the isoelectroni c, isostructural and essentially isosteric hexagonal chalcohalide rhen ium cluster monoanion, Re6S5Cl9- [5]. Taking into account our earlier observation [3] that both 1.+, and the doubly oxidized form 1(2+) are easily accessible, two types of association can be anticipated in the solid state : 1(2+) (Mo6Br142-) and (1.+)2(Mo6Br142-). Furthermore, wi th an r2/r1.+ radius ratio of 0.82, 8-coordination of the molecular an ions should occur in the solid state, affording either a CsCl structur e, for the 1:1 salt, or an antifluorite structure, for the 2:1 stoichi ometry. Likewise, a 1:1 CsCl type structure is predicted for the assoc iation of 1.+ and Re6S5Cl9-. Here we demonstrate that these prediction s are fullfilled by the title compounds, whose preparation by the elec trocrystallization technique, crystal structure analysis and single-cr ystal ESR characterization are presented.