Fluorescence quenching in Zn2+-bis-terpyridine coordination polymers: a single molecule study

Abstract

A Zn 2+ -bis-terpyridine coordination polymer is investigated by single-molecule fluorescence spectroscopy (SMS). The bis-terpyridine ligands of the coordination polymers bear conjugated chromophores connecting the terpyridine spheres of the ligands, which resemble structural features of MEH-PPV. To the best of our knowledge this paper presents the first systematic SMS study on Zn 2+ -bis-terpyridine coordination polymers. Upon incorporation of free chromophores into the polymer, the fluorescence quantum yield of individual chromophores appears to be reduced. The reason for the reduced emission per chromophore in a polymer is investigated by brightness studies on single isolated polymer molecules. Furthermore, the experiments reveal that the Zn 2+ -bis-terpyridine coordination polymer contains a significantly larger fraction of effective chromophores, compared to one of the most common conjugated polymers, e.g., MEH-PPV. This finding is attributed to the particularly rigid geometry of the system at hand, which was corroborated by polarization-dependent experiments. Time-resolved experiments identified two different types of intensity fluctuations: small amplitude intensity fluctuations might correlate with switching of individual chromophores by structural fluctuations, while large amplitude jumps switch off the emission of the entire molecule. Finally, experiments under different atmospheric conditions offer further insights into the molecular mechanism and the nature of the quenchers involved in the blinking.

Syntheses, structures, and properties of nine d10or p-block coordination polymers based on a ligand containing both terpyridyl and sulfo groups

“…As shown in Figure 1a, the asymmetric unit of 1 contains a half of Zn(II) ion on an inversion centre, one HDSPTPligand, two coordinated and three lattice water molecules. Each Zn(II) is surrounded by an 50 N 2 O 4 donor set, formed by two terpyridine nitrogen atoms from two different HDSPTPligands, and four terminal water oxygen atoms. The Zn−N bond is 2.113(6) Å.…”

“…The asymmetric unit of 3 contains two independent Ag(I) ions lying on inversion 45 centers with 0.5-occupancy, one HDSPTPanion, and three uncoordinated water molecule. Both of the Ag1 and Ag2 have similar linear coordination environment, in which the Ag(I) ion is coordinated by two pyridine N atoms and surrounded by two water molecules via Ag···O interaction (the distance is 3.064 50 and 3.204 Å) as shown in Fig. 3a.…”

“…In the SBU, four Pb1 ions are placed on the four vertices of tetrahedron with adjacent Pb···Pb seperation range from 5.749 to 6.705 Å. Each tetranuclear SBU connect to four adjacent tetranuclear SBUs via double DSPTP 2- 50 bridges, leading to a 3D framework (Fig. 9c).…”

“…11 They are negative ligands similar to carboxylate ligands and suitable for constructing MOF without small anions. The coordination geometries of sulfo group are 50 different from carboxylate group because the S atom displays sp 3 hybridization that causes the number and orientation of donor O atoms to be quite different. Moreover, the sulfo group is weaker donors making them good candidates for forming flexible host structures.…”

“…Xray powder diffraction measurements were measured by using a Bruker D8 Advance diffractometer at 40 kV, 40 mA with a Cu- 15 target tube and a graphite monochromator. 50 and H 2 O (2 mL) was sealed in a 20 mL Teflon-lined stainlesssteel reactor, heated at 120 o C for 72 hours under autogenous pressure, and then slowly cooled to room temperature at a rate of 2 o C/h. Colorless block crystals of 4 were collected by filtration and washed with ethanol several times.…”