Excimer and Red Luminescence Due to Aggregation‐Induced Emission in Naphthalene Based Zinc Phosphonate

Abstract

The phosphonate Zn(PO 3 -CH 2 -C 10 H 7 ) has been obtained as single crystals and polycrystalline powder by hydrothermal synthesis from the parent acid 1-naphthylmethylphosphonic acid H 2 PO 3 CH 2 -C 10 H 7 . This Zn phosphonate exhibits a unique layered structure (P2 1 /c), built up of single inorganic [ZnPO 3 C] layers stacked with organic bilayers of naphthylmethyl moieties "CH 2 -C 10 H 7 ". The inorganic [ZnPO 3 C] layers consist of infinite zig-zag chains of corner-sharing ZnO 4 tetrahedrons running along the b direction and interconnected through PO 3 C tetrahedrons along c. The luminescence properties of this compound show two features never observed so far in any hybrid matrix containing naphthalene ligand: excimer emission characterized by one band fitted at 403 nm; and red

M(H2O)(PO3C10H6OH)·(H2O)0.5 (M = Co, Mn, Zn, Cu): a new series of layered metallophosphonate compounds obtained from 6-hydroxy-2-naphthylphosphonic acid

“…The compounds with the transition metals Mn 2+ , Co 2+ , and Cu 2+ have shown different absorption and emission properties indicating the contribution of transition metals to those optical properties. The ligand and compounds with Mn 2+ , Co 2+ , Zn 2+ present a red shifted emission, which is relatively similar to the one observed in our previous work, 22 and which remains unexplained yet and will therefore need further investigations.…”

“…This may indicate a common origin of those bands, which could be attributable to the common naphthalene moiety into the ligand and hybrids. This kind of red shifted emission has been observed in a previous paper 22 on ligands and hybrids however, the structure of those compounds (2), (3), (4), (6) does not allow us to conclude straightforwardly the same origin of this red shifted emission.…”

“…The naphthalene moieties present in ligand (2) and hybrids (3)-(6) exhibit singlet-singlet radiative recombination from 310 to 390 nm, and under some conditions of the saturated solution, show excimer-type emission ranging from 375 to 420 nm. 22 Thus, emission bands in the range of 310 to 420 nm may be attributed to singlet-singlet recombination and to possible excimer like emission 22 originating from the naphthalene moiety in the ligand and hybrids. The band at 542 nm for Co compound (4) could be attributed to recombination occurring from the level 2 T 1g (H) to the ground level 4 T 1g (F) in the octahedral symmetry site.…”

“…2 The development of materials featuring new properties resulted from a rational choice of both organic and metal precursors. 17 The functionalization of the organic moieties allowed the introduction of new properties including coordination properties used for catalysis 18,19 and asymmetric catalysis, 20 ionic conduction, 21 and fluorescence 22 or the preparation of microporous 23 or mesoporous 24 materials. On the other hand, a rational selection of the metal ions offered properties like magnetism, 25,26 luminescence, [27][28][29] bactericidal action 30 or controlled metallic salt release.…”

“…Phenol and naphthol could present fluorescence properties as recently reported for a naphthyl phosphonic derivative. 22 Finally, phenol functions could allow the post functionalization of hybrid materials (e.g. reaction with diazonium salts) or could feature proton exchange properties due to their acidity ( pK a ≈ 9).…”