Solvent-mediated preparation of a heterometallic [2 × 2] grid via a 1D metal–organic template with extraordinary acid/base-resistance

Abstract

A new 1D coordination polymer, [Fe^IIL(H₂O)]·2H₂O (1) (H₂L = 2,6-bis[3-(pyrazin-2-yl)-1,2,4-triazoly]pyridine) with extraordinary acid/base-resistance was synthesized. It was found that the 1D metal–organic chain can serve as a template to prepare a heterometallic [2 × 2] grid [Fe^III₂Na₂L₄(H₂O)₄]·8H₂O (2) through a solvent-mediated strategy by immersing the fresh crystals of 1 in a saturated MeOH solution of NaN₃. The transformation was accompanied by the complete dissolution of the original crystals, and the cleavage/regeneration of coordination bonds. The final structure of 2 was unambiguously characterized by means of a single-crystal X-ray diffraction (SCXRD) study. Notably, L²⁻ in 1 exhibits an “acute triangle” configuration, while an “obtuse triangle” configuration is observed in 2. In addition, treatments of 1 with saturated MeOH solutions of NaF, NaCl, NaBr, NaI, and NaN₃ in DMF, EtOH, and H₂O were also respectively checked. The results did not show any appreciable indication, probably implying that the transformation kinetics is influenced not only by a sodium source but also by a solvent-exclusive effect. Significantly, the resulting grid of 2 could not be accessed by a direct one-pot self-assembly synthetic approach.