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Tetrazine Chromophore‐Based Metal–Organic Frameworks with Unusual Configurations: Synthetic, Structural, Theoretical, Fluorescent, and Nonlinear Optical Studies
Author(s) -
Li Jianghua,
Jia Ding,
Meng Suci,
Zhang Jinfang,
Cifuentes Marie P.,
Humphrey Mark G.,
Zhang Chi
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404803
Subject(s) - tetrazine , fluorescence , metal organic framework , chromophore , materials science , topology (electrical circuits) , crystallography , single crystal , fluorescence spectroscopy , spectroscopy , chemistry , photochemistry , physics , organic chemistry , mathematics , adsorption , quantum mechanics , combinatorics
Three unusual three‐dimensional (3D) tetrazine chromophore‐based metal–organic frameworks (MOFs) {(Et 4 N)[WS 4 Cu 3 (CN) 2 (4,4′‐pytz) 0.5 ]} n ( 1 ), {[MoS 4 Cu 4 (CN) 2 (4,4′‐pytz) 2 ] ⋅ CH 2 Cl 2 } n ( 2 ), and {[WS 4 Cu 3 (4,4′‐pytz) 3 ] ⋅ [N(CN) 2 ]} n ( 3 ; 4,4′‐pytz=3,6‐bis(4‐pyridyl)tetrazine) have been synthesized and characterized by using FTIR and UV/Vis spectroscopy, elemental analysis, powder X‐ray diffraction, gel permeation chromatography, steady‐state fluorescence, and thermogravimetric analysis; their identities were confirmed by single‐crystal X‐ray diffraction studies. MOF 1 possesses the first five‐connected M/S/Cu (M=Mo, W) framework with an unusual 3D (4 4 ⋅6 6 ) topology constructed from T‐shaped [WS 4 Cu 3 ] + clusters as nodes and single CN − /4,4′‐pytz bridges as linkers. MOF 2 features a novel 3D MOF structure with (4 20 ⋅6 8 ) topology, in which the bridging 4,4′‐pytz ligands exhibit unique distorted arch structures. MOF 3 displays the first 3D MOF structure based on flywheel‐shaped [WS 4 Cu 3 ] + clusters with a non‐interpenetrating honeycomb‐like framework and a heavily distorted “ACS” topology. Steady‐state fluorescence studies of 1 – 3 reveal significant fluorescence emissions. The nonlinear optical (NLO) properties of 1 – 3 were investigated by using a Z ‐scan technique with 5 ns pulses at λ =532 nm. The Z ‐scan experimental results show that the π‐delocalizable tetrazine‐based 4,4′‐pytz ligands contribute to the strong third‐order NLO properties exhibited by 1 – 3 . Time‐dependent density functional theory studies afforded insight into the electronic transitions and spectral characterization of these functionalized NLO molecular materials.