دكتوراه
العلوم والتقنية
Cardiff University
مجال التميز | تميز دراسي وبحثي |
البحوث المنشورة |
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البحث (1): | |
عنوان البحث: | Iridium(III) Sensitisers and Energy Upconversion: The Influence of Ligand Structure upon TTA‐UC Performance |
رابط إلى البحث: | https://chemistryeurope.onlinelibrary.wiley.com/doi/epdf/10.1002/chem.202004146 |
تاريخ النشر: | 26/11/2020 |
موجز عن البحث: | Six substituted ligands based upon 2‐(naphthalen‐1‐yl)quinoline‐4‐carboxylate and 2‐(naphthalen‐2‐yl)quinoline‐4‐carboxylate have been synthesised in two steps from a range of commercially available isatin derivatives. These species are shown to be effective cyclometallating ligands for IrIII, yielding complexes of the form [Ir(C^N)2(bipy)]PF6 (where C^N=cyclometallating ligand; bipy=2,2′‐bipyridine). X‐ray crystallographic studies on three examples demonstrate that the complexes adopt a distorted octahedral geometry wherein a cis‐C,C and trans‐N,N coordination mode is observed. Intraligand torsional distortions are evident in all cases. The IrIII complexes display photoluminescence in the red part of the visible region (668–693 nm), which is modestly tuneable through the ligand structure. The triplet lifetimes of the complexes are clearly influenced by the precise structure of the ligand in each case. Supporting computational (DFT) studies suggest that the differences in observed triplet lifetime are likely due to differing admixtures of ligand‐centred versus MLCT character instilled by the facets of the ligand structure. Triplet–triplet annihilation upconversion (TTA‐UC) measurements demonstrate that the complexes based upon the 1‐naphthyl derived ligands are viable photosensitisers with upconversion quantum efficiencies of 1.6–6.7 %. |
البحث (2): | |
عنوان البحث: | Spectroscopic and Theoretical Investigation of Color Tuning in Deep-Red Luminescent Iridium(III) Complexes |
رابط إلى البحث: | https://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.9b02991 |
تاريخ النشر: | 04/02/2020 |
موجز عن البحث: | A series of heteroleptic, neutral iridium(III) complexes of the form [Ir(L)2(N^O)] (where L = cyclometalated 2,3-disubstituted quinoxaline and N^O = ancillary picolinate or pyrazinoate) are described in terms of their synthesis and spectroscopic properties, with supporting computational analyses providing additional insight into the electronic properties. The 10 [Ir(L)2(N^O)] complexes were characterized using a range of analytical techniques (including 1H, 13C, and 19F NMR and IR spectroscopies and mass spectrometry). One of the examples was structurally characterized using X-ray diffraction. The redox properties were determined using cyclic voltammetry, and the electronic properties were investigated using UV–vis, time-resolved luminescence, and transient absorption spectroscopies. The complexes are phosphorescent in the red region of the visible spectrum (λem = 633–680 nm), with lifetimes typically of hundreds of nanoseconds and quantum yields ca. 5% in aerated chloroform. A combination of spectroscopic and computational analyses suggests that the long-wavelength absorption and emission properties of these complexes are strongly characterized by a combination of spin-forbidden metal-to-ligand charge-transfer and quinoxaline-centered transitions. The emission wavelength in these complexes can thus be controlled in two ways: first, substitution of the cyclometalating quinoxaline ligand can perturb both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital levels (LUMO, Cl atoms on the ligand induce the largest bathochromic shift), and second, the choice of the ancillary ligand can influence the HOMO energy (pyrazinoate stabilizes the HOMO, inducing hypsochromic shifts). |
المؤتمرات العلمية |
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المؤتمر (1): | |
عنوان المؤتمر: | SPECTROSCOPY AND DYNAMICS GROUP MEETING 2020 |
تاريخ الإنعقاد: | 06-08/01/2020 |
مكان الإنعقاد: | University of Warwick. UK |
طبيعة المشاركة: | Poster presentation |
عنوان المشاركة: | A spectroscopic and theoretical investigation of color tuning in luminescent iridium (III) complexes |
ملخص المشاركة: | A combined spectroscopic and computational study has been used to characterise a range of iridium complexes for use as potential tunable OLED phosphors or up conversion donors. This characterisation has been performed through the use of absorption/emission spectroscopy, transient absorption spectroscopy and is supported by DFT analysis. |