Non-covalent O···O interactions among isopolyanions using a cis-{MoO₂} moiety by the assistance of N-H···O hydrogen bonds

Abstract

An inorganic-organic hybrid material, [2-AmpH]₄[Mo₈O₂₆] (1) has been isolated by the reaction of Na₂MoO₄·2H₂O with 2-aminopyrimidine (2-Amp) from an acidic aqueous medium. In this low pH synthesis, the organic molecule (2-Amp) gets mono-protonated (2-AmpH⁺) and acts as the cation in stabilizing the octamolybdate anion in 1. Compound 1 crystallizes in the triclinic space group P-1 with α = 9·925(3), b = 10·020(3), c = 10·414(3) Å, α = 88·811(4), β = 64·907(4), γ = 89.506(4)°, Z = 1. An interesting three-dimensional supramolecular structure, having well-defined channels, is formed through N-H···O and C-H···O hydrogen bonds, in which the protonated organic cation plays a significant role. The crystal structure also reveals an unusual cluster-cluster (non-covalent O···O) interaction using cis-(MoO₂} moieties of the isopolyanion. N-H···O hydrogen bonds, originated from pyridimidinium cation and isopolyanion, are found to influence to attain such non-covalent O···O interactions among polyoxometalate anions. An interesting helical arrangement, formed from isopolyanion and organic cation, is observed.