pH-Dependent Ag(<scp>i</scp>) coordination architectures constructed from 4-cyanopyridine and phthalic acid: from discrete structure to 2D sheet

Abstract

Four mixed-ligand Ag(I) coordination complexes (CCs), namely, [Ag(cnpy)2(Hpta)] (1), [Ag2(cnpy)2(Hpta)2] (2), [Ag4(cnpy)2(pta)2(H2O)]n (3) and [Ag2(inta)2(pta)·3H2O]n (4), (cnpy = 4–cyanopyridine, H2pta = phthalic acid, inta = isonicotinamide) have been synthesized through a one-pot ultrasonic reaction of silver(I) oxide, cnpy and H2pta under different pH values and structurally characterized. Complexes 1 and 2 formed at lower pH values (5.0 for 1 and 6.9 for 2) exhibit zero-dimensional (0D) mononuclear and tetranuclear motifs, respectively. Reaction at pH = 8.8 leads to a two-dimensional (2D) structure of 3 in which completely deprotonated H2pta shows two kinds of coordination modes: μ5-η1:η1:η1:η3 and μ6-η1:η1:η1:η3. A further increase of the pH value to 9.4 results in the in situhydrolysis of cnpy and produces complex 4 as a one-dimensional (1D) chain structure. Of particular interest, a well-resolved chair-like centrosymmetric hexamer water cluster, (H2O)6, which is stabilized by 1D chains through six dangling hydrogen bonds, exists in 4. Comparing the experimental results, it is comprehensible that the pH value plays a crucial role in the formation of the resulting structures. Additionally, results about IR spectra, thermogravimetric curves and photoluminescence spectra were discussed.