Substituent regulated photoluminescent thermochromism in a rare type of octahedral Cu4I4 clusters
| Autor: | Guang-Hui Chen, Ling-Bin Meng, Qiu-Cheng Chen, Xiao-Chun Huang, Ya-Dong Yu |
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| Rok vydání: | 2018 |
| Předmět: |
Steric effects
Thermochromism Photoluminescence 010405 organic chemistry Substituent General Chemistry 010402 general chemistry 01 natural sciences Catalysis 0104 chemical sciences chemistry.chemical_compound Crystallography chemistry Excited state Materials Chemistry Hypsochromic shift Pyridinium Phosphorescence |
| Zdroj: | New Journal of Chemistry. 42:8426-8437 |
| ISSN: | 1369-9261 1144-0546 |
| DOI: | 10.1039/c8nj00505b |
| Popis: | A series of Cu4I4 clusters (1–5) supported by two pyrazolate-type zwitterionic ligands N-methyl-[4-(5-R-pyrazolyl)]pyridinium (1: R = tert-butyl; 2: R = trifluoromethyl; 3, 4, 5: R = phenyl) have been prepared and fully characterized. These compounds all exhibit a distorted “octahedral” geometry and their luminescence behavior is quite distinct from those of previously reported tetranuclear copper halide clusters. The crystalline powders of all five clusters only show a single broad low-energy (LE) emission band from 300 to 80 K. Cluster 1 shows temperature-independent orange phosphorescence despite a slight blue-shift of the low-energy flank upon cooling. Intriguingly, for clusters 2–5, a hypsochromic phenomenon is clearly observed by decreasing the temperature. Using DFT/TDDFT calculations, we find that the nature of the electronic transitions responsible for the LE emission is dominated by the steric demand and/or electronic characteristics of the substituents on the pyrazolyl moiety. Specially, contribution of cuprophilic interactions in the lowest triplet excited states is ruled out by the rigid ligands. The single LE emission of 1 and 2 is attributed to pure 3ILCT and 3(M + X)LCT transitions, respectively, while the emission of 3 and 4 is assigned to a mixed 3ILCT and 3(M + X)LCT transition with different proportions. |
| Databáze: | OpenAIRE |
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