Dabco

Hoechst33342 staining was used to visualize nuclear condensation. Cells plated on coverslips were fixed with 4% paraformaldehyde (w/v) in PBS at room temperature for 10 min. Fixed cells were then incubated with Hoechst33342 (500 ng/mL in PBS) at room temperature for 20 min. Coverslips were mounted using DABCO solution (0.5% DABCO (D27802, Merck KGaA), 90% glycerol in 10 mM Tris/HCl (pH 7.4)). Fluorescent images were obtained using a BZ-X700 fluorescence microscope (KEYENCE CORPORATION, Osaka, Japan).

Thermoplastic polyurethane was prepared using two-step method, also called prepolymer method. In the first step (Figure 1), urethane prepolymer was synthesized using 4,4′-diphenylmethane diisocyanate (MDI, BorsodChem, Kazincbarcika, Hungary) and ester-based polyol, i.e., α,ω-oligo(ethylene-butylene adipate)diol (POLIOS 55/20, Purinova, Bydgoszcz, Poland), which is characterized by average molecular weight around 2000 g mol⁻¹, hydroxyl number 58 mg KOH g⁻¹ and acid number 0.3 mg KOH g⁻¹. The synthesis of prepolymer was carried out at 80 °C for 2 h (under the vacuum) and resulted polymer was characterized by the amount of unreacted isocyanate groups equal 7.2 wt%.
In the next step (Figure 2) prepolymer was reacted with chain extender, i.e., 1,4-butanediol (Brenntag, Kędzierzyn-Koźle, Poland). The reaction was catalyzed using 1,4-diazabicyclo[2.2.2] octane (DABCO, Sigma Aldrich, Saint Louis, MO, USA), which was previously dissolved in the chain extender (to obtain 0.3 wt% solution of DABCO in BDO). The molar ratio of [NCO]/[OH] groups during prepolymer chains extending step was equal 0.95). Finally, obtained material was seasoned at 100 °C for 24 h.

Zn(NO₃)₂·6H₂O (0.030 g, 0.1 mmol, Aldrich), 3,3′-PDBA (0.032 g, 0.1 mmol), and 1,4-diazabicyclo[2,2,2]octane (DABCO) (0.006 g, 0.05 mmol, Aldrich) were dissolved in 5 mL of DMF and heated at 120 °C for 4 d. Transparent colorless block crystals were retrieved by filtration and washed with DMF. The crystals were dried in air (~ 0.024 g). High-quality block crystals were directly chosen for single-crystal X-ray crystallography from the as-prepared sample. Analytical analysis calculated for C₅₁H₅₄N₉O₁₁Zn₂ (1099.81): C 55.70, H 4.95, N 11.46; found C 55.27, H 4.40, N 10.67%.