Self-Assembled Tetrahedral [CrIII4L6]12+ Cage Displaying Near-Infrared Spin-Flip Photoluminescence
Year: 2024
Type: article
Abstract: The thermodynamically controlled self-assembly of bis-bidentate quaterpyridine ligand, L = 2,2′:5′,5″:2″,2‴-quaterpyridine, with Cr II and subsequent oxidation to Cr III yields the first photoluminescent tetrahedral [Cr III 4 L 6 ] 12+ molecular cage. Single-crystal X-ray diffraction reveals the presence of two homochiral cages (ΛΛΛΛ and ΔΔΔΔ) in the unit cell that crystallize as a racemic mixture. Additionally, a PF 6 anion is observed inside the cavity, in line with isostructural cages built with Ni II or Fe II . Each corner of the polyhedron is occupied by weakly antiferromagnetically coupled {Cr(bipy) 3 } 3+ (bipy = 2,2′-bipyridine) patterns, as revealed by magnetometry. Upon light excitation in the UV–vis region, spin-flip luminescence from the 2 E/ 2 T 1 excited states with a maximum at 727 nm (13755 cm –1 ) was detected at room temperature. The measured excited state lifetime of 183 μs is longer than the 102 μs recorded for the mononuclear [Cr(bipy) 3 ] 3+ complex under anaerobic conditions, whereas the luminescence quantum yields are in the same order of magnitude and amount to 10 –2 %. The photoluminescence brightness, B, calculated using the maxima of the absorption spectra for both species, goes from 14 M –1 ·cm –1 for the mononuclear compound to 90 M –1 ·cm –1 for the tetrahedral cage. This 6-fold improvement is observed across the entire excitation wavelength range, and it is due to the incorporation of four light-harvester units in the molecular cage.
Source: Inorganic Chemistry
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Awards: G1092424111, G1157807336, G1175115578, G121809054, G1401168639, G1495698476, G1622782223, G1855990336, G210041235, G2114305129, G2153988870, G2262748287, G2309174360, G2601397997, G2642559387, G2660406951, G279363373, G2863668859, G300979063, G34346518, G3472979172, G3480869486, G3518538256, G3641559371, G3681454997, G4042783231, G410571670, G421066526, G423461254, G425668148, G430777504, G4397845884, G4442677895, G451917667, G4526231891, G4793495473, G5080475149, G5178866988, G5195188938, G5338730000, G5421974903, G545522889, G5539308778, G5967599077, G6033112984, G66099019, Supramolecular Capsules and Cages for Circularly Polarized Luminescence, G7084143925, G7092120783, G8920660035, G897484643, G929308097, G99296377
OpenAlex ID: W4404799537