Complexation of triangular silver(i) or copper(i) nitropyrazolates with dibenzothiophenes having potential use in adsorptive desulfurization†
Abstract
Triangular silver(I) and copper(I) 3,5-diethyl-4-nitropyrazolates (abbreviated as [Ag(denpz)]3 or Ag3pz3, and [Cu(denpz)]3 or Cu3pz3), as well as their adducts with dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (DMDBT) and benzothiophene (BT), have been prepared and characterized by a series of techniques. X-ray analyses show that these adducts are stabilized by M⋯S, M⋯C contacts and π⋯π stacking interactions. NMR measurements and theoretical calculations indicate that the intensity of interaction between the metal complexes and dibenzothiophenes follows the trend: Ag3pz3–DMDBT > Ag3pz3–DBT > Cu3pz3–DMDBT > Cu3pz3–DBT, which can be understood on the basis of a weak interaction between π-acid (Ag3pz3 or Cu3pz3) and π-base (DBT/DMDBT). Both complexes show good adsorptive ability and reusability toward the removal of DBT and DMDBT from model oil (n-octane), with the maximum adsorption capacity at room temperature being 39 mg S (DMDBT) per g Cu3pz3, 34 mg S (DMDBT) per g Ag3pz3, 40 mg S (DBT) per g Cu3pz3, 36 mg S (DBT) per g Ag3pz3, respectively. Compared to Ag3pz3, Cu3pz3 exhibits higher adsorptive capacities for DBT/DMDBT, which has been attributed to its lower molecular mass.