Thallium(I) Tropolonates: Synthesis, Structure, Spectral Characteristics, and Antimicrobial Activity Compared to Lead(II) and Bismuth(III) Analogues

Abstract

Synthesis, single-crystal X-ray determination diffraction and FT-IR, NMR (¹H, ¹³C, ¹⁹F and ²⁰⁵Tl), UV-vis, and luminescence spectra characteristics were described for series of thallium(I) compounds: thallium(I) triflate (Tl(OTf)), 1:1 co-crystals of thallium(I) triflate and tropolone (Htrop), Tl(OTf)·Htrop, as well as simple thallium(I) chelates: Tl(trop) (1), Tl(5-metrop) (2), Tl(hino) (3), with Htrop, 5-methyltropolone (5-meHtrop), 4-isopropyltropolone (hinokitiol, Hhino), respectively, and additionally more complex {Tl@[Tl(hino)]₆}(OTf) (4) compound. Comparison of their antimicrobial activity with selected lead(II) and bismuth(III) analogs and free ligands showed that only bismuth(III) complexes demonstrated significant antimicrobial activity, from two- to fivefold larger than the free ligands.

Keywords: 5-methyltropolone; antimicrobial activity; crystal structure; hinokitiol; thallium(I) complexes; thallium(I) triflate; tropolone.

Figure 1

A fragment of the crystal structure of thallium(I) triflate showing the near surroundings around thallium(I) ions (atoms, except for O3–O6 and C1, shown as 50% ellipsoids).

Figure 2

A fragment of the crystal structure of Tl(OTf)·Htrop adduct showing the near surroundings around the thallium(I) ion (nonhydrogen atoms shown as 50% ellipsoids).

Figure 3

Molecular structures of Tl(trop) (1) (left) and Tl(5-metrop) (2) (right) (symmetry code: (i) −x + 1, y, −z + 1.5). Nonhydrogen atoms are shown as 50% ellipsoids.

Figure 4

Coordination spheres of thallium(I) ions in complexes: (a) 1 and (b) 2 (symmetry codes as in Table 2). Solid and dashed lines indicate chelating bonds and intermolecular contacts, respectively.

Figure 5

Two different views of the arrangement of Tl(trop) chelates in the extended structure of 1 showing the chosen intermolecular Tl···O contacts.

Figure 6

Two different views of the arrangement of Tl(5-metrop) chelates in the extended structure of 2 showing the chosen intermolecular contacts.

Figure 7

Asymmetric unit of 3 with intermolecular contacts between Tl(hino) molecules (atoms shown as 50% ellipsoids; hydrogen atoms were omitted for clarity).

Figure 8

Asymmetric unit of 4 in two different views showing intermolecular contacts between Tl(hino) molecules (black dotted lines) and the shortest distances for the free Tl⁺ ion (blue dotted lines). Atoms are shown as 50% ellipsoids. Hydrogen atoms and the triflate ion were omitted for clarity.

Figure 9

Coordination spheres of thallium(I) ions in compounds (a) 3 (symmetry codes as in Table 3) and (b) 4 (symmetry codes as in Table 4). Solid and dashed lines indicate chelating bonds and intermolecular contacts, respectively.

Figure 10

The arrangement of molecules in the extended structures of (a) 3 and (b) 4.

Scheme 1

Atom labeling in tropolonato-like ligands used for NMR assignments.