Proton‐Switched Emission Behavior of Hexanuclear Molyb‐denum(II) Clusters Bearing Terminal Pyridine Carboxylate Ligands

Abstract

We designed and synthesized a new and novel octahedral hexamolybdenum(II) cluster bearing terminal pyridine‐3‐carboxylate (3L) or pyridine‐4‐carboxylate ligands (4L), [{Mo6Br8}(3L)6]2– (3) or [{Mo6Br8}(4L)6]2– (4), to demonstrate proton‐switched emission behaviour of the cluster. X‐ray crystal analysis of 4 demonstrated that the O‐atom in the carboxylate group of 4L coordinates to each Mo atom in the {Mo6Br8}4+‐core, indicating that the N‐atom of 4L in 4 is open for protonation. Reflecting such structural characteristics of the cluster, both 3 and 4 showed proton‐switched emission behaviour owing to the changes in the electron‐donating abilities of the relevant terminal ligands upon protonation to the pyridine N atoms: blue shifts of the emission spectra and increases in the emission lifetimes of the clusters.

Supramolecular hybrids based on Ru(ii) porphyrin and octahedral Mo(ii) iodide cluster

“…Inspired by this approach, we have recently combined, in a single system, 26 an A 2 -type zinc porphyrin, 5,15-bis[( ptolyl)porphyrinato (2-)]zinc, and an octahedral Mo(II) iodide cluster functionalized with pendant isonicotinate moieties ((Bu 4 N) 2 [{Mo 6 I 8 }(OOC-C 5 H 4 N) 6 ]) (PyMoC). [27][28][29][30] Such hexanuclear molybdenum clusters are of particular interest for making supramolecular hybrids, since the hexamolybdenum core Mo 6 I 8 can be easily modified with different octahedrally arranged functional groups. 27,31 Thus, the [{Mo 6 I 8 } (OOC-C 5 H 4 N) 6 ] 2− cluster anion with six donor nitrogen atoms acts as a hexatopic polypyridine ligand.…”

Expanding the Toolbox of Octahedral Molybdenum Clusters and Nanocomposites Made Thereof: Evidence of Two-Photon Absorption Induced NIR Emission and Singlet Oxygen Production

“…Octahedral transition metal cluster based compounds of general formula A x M 6 X i 8 L a 6 (A = monovalent cation, x = 2 for M = Mo or W or x = 4 for M = Re, X i = halogen or chalcogen inner ligand, and L a = anionic apical ligand) have attracted the attention of many research groups this past decade for their abilities to emit in the red–NIR and produce singlet oxygen upon either UV–vis or X-ray irradiation. − Many studies have described their potential in cancer treatment, , bioimaging, optoelectronics, − lighting, , solar concentrators, , anticouterfeiting, oxygen sensors, − or photocatalysis . Herein, we demonstrate the ability of A 2 Mo 6 I i 8 (OCOC 2 F 5 ) a 6 (A = alkali or organic cation) to emit red–NIR light and generate singlet oxygen upon NIR excitation by a two-photon absorption (TPA) process.…”