A new 3D HoIII-organic framework constructed from 1,3,5-tris(4-carboxy-phenyl)benzene and 1,10-phenanthroline: Crystal structure, morphological and solid state luminescence properties

Abstract

A new polynuclear LnIII coordination compound (1) with the stoichiometric formula {[Ho(BTB)(phen)]⋅(DMF)}n, (H3BTB ¼ 1,3,5-Tris(4-carboxyphenyl)benzene, phen ¼ 1,10 –phenanthroline monohydrate and DMF ¼ N, N – dimethylformamide) has been synthesized by the solvothermal method and characterized by the infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction studies, elemental analysis and solid-state electronic absorption properties and solid-state photoluminescence measurements. The XRD analyses indicate that 1 crystallizes in a monoclinic system with space group P21/c and also each HoIII ion has eight coordination, forming a distorted square antiprismatic geometry. For all the coordinated oxygen atoms, six of them belong to five carboxylate groups from different BTB3ligands, while two nitrogen atoms from only one phen ligand were involved in the coordination. Two crystallographically equivalent HoIII ions are bridged to a dimeric unit as secondary unit buildings (SUBs) by four carboxyl groups in different directions, which also form typical 1D hexagonal channels with BTB3 ligands, these channels are connected in a three-dimensional (3D) framework. Also, these open channels were occupied by two different BTB3 ligands. According to the 3D Hirshfeld surface and 2D fingerprint plots analysis, H⋯H intermolecular interactions are the dominant interactions in the HoIII. Additionally, the π⋯π stacking information determined by the shape index and curvedness plots coincides with the crystal structure analysis. Moreover, photoluminescence properties of 1 were recorded and investigated at room temperature in the Vis-NIR region. Under the excitation of UV light, 1 exhibited strong yellowish-orange emission with CIE chromaticity coordinates (0.480, 0.430). 1 emits at 521, 575 and 653 nm correspond to 5 F3 → 5 I8, 5 S2 þ5 F4→ 5 I8 and 5 F5→ 5 I8 in the visible region, whereas only one weakly peak at 761 nm originated to 5 S2 þ5 F4→ 5 I7 in the NIR region. This polymeric complex can potentially be applied to luminescent probes or OLEDs.