A series of metal-organic polymers assembled from MCl2 (M = Zn, Cd, Co, Cu): structures, third-order nonlinear optical and fluorescent properties

In this paper four metal-organic polymers {[Zn(fcz)Cl-2]center dot CH3OH}(n) 1, {[Cd(cz)(2)Cl-2]center dot CH3OH center dot 2H(2)O}(n) 2, {[Co(fcz)(2)Cl-2]center dot 2CH(3)OH}(n) 3 and {[Cu(fcz)(2)Cl-2]center dot 2CH(3)OH}(n) 4 ( fcz = fluconazole: alpha-(2,4-difluorophenyl)-alpha-(1H-1,2,4-triazol-1-ylmethyl)-1H-1,2,4-triazole-1-ethanol) were synthesized and characterized by X-ray single crystal diffraction. Polymer 1 consists of 1-D infinite chains arranged along the b-axis. All of polymers 2-4 exhibit a 2-D rhombohedral grid structure. We study the third-order nonlinear optical properties of fcz and polymers 1-4 in DMF solution by using 8 ns laser pulses at 532 nm, and find that 1 and 4 exhibit different NLO properties from fcz and both 2 and 3 show similar NLO properties to fcz. 1 possesses strong NLO refractive effects and large NLO absorptive behaviors. 2, 3 and fcz exhibit strong refractive effects, but their NLO absorptive behaviors are weaker than that of 1. The NLO effects of 4 are very weak. The study of optical limiting (OL) effects by using 40 ps laser pulses at 532 nm shows that fcz and polymer 3 possess a strong OL effect. The optical limiting threshold values of 0.15 J cm(-2) for fcz and 0.16 J cm(-2) for 3 are comparable to those of many heterothiometallate clusters. Polymers 1, 2 and 4 show a weak OL effect. The fluorescent spectra in DMF solution (concentration: 1 x 10(-4) mol dm(-3)) show that polymers 1-4 exhibit different luminescence properties from fcz. The maximum wavelength of polymers 1-3 are blue shifted gradually by 2-12 nm while polymer 4 exhibits a fluorescent self-quenching phenomenon. These results demonstrate that metal ions play an important part in the NLO and fluorescent properties of coordination polymers.