Triazolyl–Based Copper–Molybdate Hybrids: From Composition Space Diagram to Magnetism and Catalytic Performance

Abstract

The multicomponent mixed-metal Cu(II)/Mo(VI) oxides/1,3-bis(1,2,4-triazol-4-yl)adamantane (tr2ad) system was thoroughly studied employing a compositional diagram approach. The concept allowed us to prepare three layered copper-molybdate hybrid solids [Cu(II)2(tr2ad)4](Mo8O26) (1), [Cu4(II)(μ4-O)(tr2ad)2(MoO4)3]·7.5H2O (2), and [Cu(I)2(tr2ad)2](Mo2O7)·H2O (3), and to elucidate the relationship between initial reagent concentration/stoichiometry and the stability of the resultant structural motifs. Compounds 1 and 2 were found to dominate throughout a wide crystallization range of the concentration triangle, whereas compound 3 was formed by redox processes in the narrow crystallization area having a high excess of Cu(OAc)2·H2O. Independent experiments carried out with Cu(OAc)2 and (NH4)6Mo7O24 in the absence of tr2ad, under the same conditions, revealed the formation of low-valent and bimetallic oxides, including Cu2O, MoO2, Cu(Mo3O10)·H2O, and Cu3(MoO4)2(OH)2. Compounds 1 and 2 show high thermal and chemical stability as examined as catalysts in the epoxidation of cis-cyclooctene and the oxidation of benzyl alcohol (BzOH) with different types of oxidants. The oxidation reaction of BzOH using tert-butyl hydroperoxide (TBHP) as the oxidant, in the presence of 1 or 2, led to benzaldehyde and benzoic acid (PhCO2H), with the latter being formed in up to 90% yield at 24 h. The results suggest that 1 and 2 may be favorable heterogeneous catalysts for the synthesis of PhCO2H. Whereas compound 1 only reveals a weak ferromagnetic coupling between neighboring Cu(II) centers (J = 0.41 cm(-1)), compound 2 shows distinct intracluster antiferromagnetic exchange interactions (J = -29.9 cm(-1), J' = -25.7 cm(-1)), which consequently results in a diamagnetic ground state.

Metal–organic frameworks in Germany: From synthesis to function

“…Hence, their coordination chemistry formally resembles that of neutral 1,2-diazole ligands and shall not be reviewed here any further. Illustrative examples of frameworks derived from this approach include bitopic linkers such as 4-(4H-1,2,4-triazol-4-yl)benzoic acid [83,84,85] or polytopic triazole linkers containing an adamantyl backbone [86,87].…”

Applications of inorganic‐organic hybrid architectures based on polyoxometalates in catalyzed and photocatalyzed chemical transformations

“…Molybdenum and copper have been previously used as efficient catalysts for the oxidation of alcohols to the corresponding carbonyl compounds . Lysenko and co‐workers designed and synthesized two mixed molybdenum‐copper heterogeneous catalysts, namely [Cu II 2 (tr 2 ad) 4 ](Mo 8 O 26 ) and [Cu II 4 (μ 4 ‐O)(tr 2 ad) 2 (MoO 4 ) 3 ]•7.5H 2 O(tr 2 ad = 1,3‐bis(1,2,4‐triazol‐4‐yl)adamantane) . These compounds showed high thermal and chemical stability and were used as catalysts in the efficient oxidation of benzyl alcohol in the presence of different types of oxidants.…”

Synthesis, Crystal Structure, and Luminescence of Cadmium(II) and Silver(I) Coordination Polymers Based on 1,3-Bis(1,2,4-triazol-1-yl)adamantane

“…Coordination polymers and metal-organic frameworks in particular are promising materials with a wide range of potential applications-gas storage and separation [11,12], enantioselective catalysis [13,14], supramolecular systems design [15], pollutant sensing [16,17], water purification [18], fabrication of electrochemical devices [19,20], and biological activity [21]. Coordination polymers based on 1,3-bis(1,2,4-triazol-4-yl)adamantane with Mo(IV), Cu(II), Zn(II), Cd(II), Ag(I), bimetallic Ag(I)/V(V), and Cu(II)/Mo(IV) were successfully synthesized and characterized by Domasevitch research group [22][23][24][25][26][27][28][29][30][31], but the coordination chemistry of its isomer, 1,3-bis(1,2,4-triazol-1-yl)adamantane remained unexplored.…”