Complexation of triangular silver(I) or copper(I) nitropyrazolates with dibenzothiophenes having potential use in adsorptive desulfurization.

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 MS, MC contacts and ππ 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.