Octa- and Tetradecanuclear Mixed-Valent Vanadium(III/IV) Malates with Triazoles: Gas Adsorptions, Chiral Interface Recognition, and In Situ Decarboxylation.

Spontaneous resolution has been found for a pair of cage-like octanuclear mixed-valent vanadium(III/IV) malate enantiomers [Δ-V III 4 V IV 4 O 5 ( R -mal) 6 (Hdatrz) 6 ]·44.5H 2 O (Δ R - 1 ) and [Λ-V III 4 V IV 4 O 5 ( S -mal) 6 (Hdatrz) 6 ]·38.5H 2 O (Λ S - 1 , H 3 mal = malic acid; Hdatrz = 3,5-diamino-1,2,4-triazole). Their racemic reduced product K 7 [V III 5 V IV 3 O 5 ( R , S -mal) 6 (trz) 6 ]·17H 2 O ( 2 ) and tetradecanuclear species K 11 [V III 3 V IV 11 O 11 ( R , S -mal) 12 (atrz) 6 ]·45.5H 2 O ( 3 ) (Htrz = 1,2,3-triazole, Hatrz = 3-amino-1,2,4-triazole) have also been obtained. In situ decarboxylation happens for 3-amino-1,2,4-triazole-5-carboxylic acid (H 2 atrzc) to yield 3-amino-1,2,4-triazole under hydrothermal conditions. Both 1 and 2 show an interesting bicapped-triangular-prismatic {V 8 O 5 (mal) 6 } building block, which further decorates symmetrically with three [V IV 2 O 2 ( R , S -mal) 2 ] 2- units to construct a pinwheel-like {V 14 }-cluster, 3 . Bond valence calculation sum (BVS) analyses manifest that the oxidation states of bicapped V atoms are +3 in 1-3 , while the other V atoms in the {V 6 O 5 } core are ambiguous between +3 and +4 states with strong electron delocalization. Intriguingly, the triple helical chains in 1 associate in parallel to generate an amine-functionalized chiral polyoxovanadate (POV)-based supramolecular open-framework. The diameter of the interior channel is 13.6 Å, showing preferential adsorption of CO 2 over gases N 2 , H 2 , and CH 4 . Importantly, homochiral framework Δ R - 1 is capable of performing chiral interface recognition for R -1,3-butanediol ( R -BDO) through host-guest interactions, as confirmed by the structural analysis of the host-guest complex Δ R - 1 ·3( R -BDO). There are six R -BDO molecules in the channel of Δ R - 1 .