Two new 5-mercapto-1-phenyl-1H-tetrazole-based Cu(I) coordination polymers with double layer structures: Crystal structures, substituent effects and sensing responses to NACs

Abstract

During the construction of coordination compounds, a minor variation in the steric and electronic characteristics of the substituent on a ligand might have a great impact on the structures and properties of the target compounds. To investigate this issue, two new coordination polymers with double layer structures, [Cu2(MPTZ)I]n (1) and {[Cu(MHPTZ)]·0.5H2O}n (2), have been successfully synthesized through the reactions of CuI and the sulfhydryl tetrazole derivatives (HMPTZ ​= ​5-mercapto-1-phenyl-1H-tetrazole and HMHPTZ ​= ​5-mercapto-1-(4-hydroxyphenyl)- 1H-tetrazole) and characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, infrared spectra and thermogravimetric analysis. In compounds 1 and 2, both (MPTZ)- and (MHPTZ)- coordinate with four Cu(I) ions with distorted tetrahedral geometry in the same coordination modes (μ4-1қN3, 2қN4, 3қS1, 4қS1) to construct the similar two-dimensional (2D) double-layer structures, however, different substituents on ligands have important effects on the introduction of iodide ions and supramolecular forces. For compound 1, a 2D inorganic wavy (CuI)n cationic double-layer structure containing Cu2I2 secondary structural unit with the Cu⋯Cu distance of 2.65 ​Å is observed, but I¯ anions are not involved in the coordination with Cu(I) in compound 2. The difference in crystal structures and compositions of compounds 1 and 2 leads to changes of their fluorescence properties. Compound 1 shows the apparent yellow emission with the maximum at 558 ​nm when exciting at 352 ​nm, which shows sensitive luminescence quenching response to nitrobenzene compounds. However, fluorescent signals of compound 2 were not monitored under UV illumination or on fluorescence spectrophotometer. The results indicate that a minor variation in the substituent on a ligand has a great impact on the structures and properties of the target coordination compounds.