Syntheses, crystal structures, and fluorescence properties of two new copper phosphonates from hydroxy-functionalized bisphosphonic acid ligand

Abstract

Exploring metal phosphonates with new crystal structures is of significance for the development of metal-organic frameworks (MOFs). In this work, two new copper phosphonates, [tetraauqa-1,4-phenylenebis(hydroxymethylene))bisphosphonate biscopper(II)] bishydrate [Cu₂(H₂L)(H₂O)₄]·2H₂O (1) and 1,4-phenylenebis(hydroxymethylene))bisphosphonate-(4,4’-bipy) copper(II) [Cu(H₄L)(4,4’-bipy)] (2) (4,4’-bipy = 4,4’-bipyridine), have been synthesized from a hydroxy functionalized bisphosphonate ligand, H₆L = (1,4-phenylenebis(hydroxymethylene))bis(phosphonic acid). The introduction of a hydroxy group can regulate the crystal structures. The bisphosphonate ligand in 1 is hexadentate, binding six copper ions with its six phosphonate oxygen atoms and two hydroxy oxygen atoms, forming a three-dimensional framework structure with rectangle channels running along the b-direction. For 2, the bisphosphonate ligands are double deprotonated and chelate or bridge two copper ions, showing a two-dimensional layered crystal structure. These compounds have interesting fluorescence properties with emission maxima (307 and 410 nm) lying in the blue region.

Keywords:

• Phosphonates
• Synthesis
• Crystal structure
• Luminescence

Supplementary material

Supplementary data related to this article can be found online.

Acknowledgment

This work was supported by the Project of Shandong Natural Science Foundation (ZR2021QB099), the Experimental Technology Research Project of Qingdao Agricultural University (SYJS202213), the National Innovation and Entrepreneurship Training Program for College Students (202210435040, S202210435074).

Disclosure statement

No potential conflict of interest was reported by the authors

Additional information

Funding

This work was supported by the Project of Shandong Natural Science Foundation (ZR2021QB099), the Experimental Technology Research Project of Qingdao Agricultural University (SYJS202213), the National Innovation and Entrepreneurship Training Program for College Students (202210435040, S202210435074).