1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane: the smallest tetrahedral tetrazole-functionalized ligand and its complexes formed by reaction with anhydrous M(ii)Cl2 (M = Mn, Cu, Zn, Cd)†‡
Abstract
1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane (H4L) was probed as a building block for the synthesis of tetrazolato/halido coordination polymers with open-network structures. MCl2 (M = Cu, Cd, Zn, Mn) was reacted with H4L in DMF at 70 °C to yield [Cu4Cl4L(DMF)5]·DMF, 1; [Cd4Cl4L(DMF)7]·DMF, 2; [Zn3Cl2L(DMF)4]·2DMF, 3 and [Mn2L(DMF)2(MeOH)4]·DMF·2MeOH·2H2O, 4. 1 and 2 (Fddd) are nearly isostructural and have zeolitic structures with a {43·62·8}, gis or gismondine underlying net, where the role of the tetrahedral nodes is served by the coordination bonded clusters and the adamantane moiety. 3 (P21/n) has a porous structure composed of coordination bonded layers with a (4·82) fes topology joined via trans-{Zn(tetrazolate)2(DMF)4} pillars with an overall topology of {4·62}{4·66·83}, fsc-3,5-Cmce-2. 4 (Pca21) is composed of stacked {Mn2L} hexagonal networks. In 1 and 2 the ligand fulfills a symmetric role of a tetrahedral building block, while in 3 and 4 it fulfills rather a role of an effective trigonal unit. Methanol-exchanged and activated 1 displayed an unusual type IV isotherm with H2 type hysteresis for N2 sorption with an expected uptake at high P/P0, but with a smaller SBET = 505.5 m2 g−1 compared to the calculated 1789 m2 g−1, which is a possible result of the framework's flexibility. For H2 sorption 0.79 wt% (1 bar, 77 K) and 0.06 wt% (1 bar, RT) uptake and Qst = −7.2 kJ mol−1 heat of adsorption (77 K) were recorded. Weak antiferromagnetic interactions were found in 1 and 4 with J1 = −9.60(1), J2 = −17.2(2), J3 = −2.28(10) cm−1 and J = −0.76 cm−1 respectively. The formation of zeolitic structures in 1 and 2, the concept of structural ‘imprinting’ of rigid building blocks, and design opportunities suggested 4 as a potential hexafunctionalized biadamantane building block.