Coordination Chemistry and Luminescence Modulation of Gold(I)-Copper(I) and Copper(I) Halide Complexes
Loading...
Authors
Chen, Kelly
Issue Date
2015
Type
Dissertation
Language
Keywords
Alternative Title
Abstract
The dissertation describes the coordination chemistry and luminescence modulation of Au(I)-Cu(I) and Cu(I) halide complexes. In Chapter 2, a series of trigonal Au(I)-Cu(I) pseudopolymorphs with emissions ranging from blue to yellow is reported. The Au(I) phosphine complex [Au(PPh2py)3]BF4 (1BF4) was prepared by the addition of tetrahydrothiophenegold(I) chloride to PPh2py with excess NaBF4 in dichloromethane/methanol. The addition of [Cu(NCCH3)4]BF4 to 1BF4 in acetonitrile produces the trigonal species [AuCu(PPh2py)3](BF4)2 (2). The luminescent pseudopolymorphs, blue-2BF4, green-2BF4, and yellow-2BF4, were obtained from the same crystallization conditions in addition to red-luminescent crystals of [Au3Cu2(PPh2py)5](BF4)5 (3). Electronic structure calculations indicated that the subtle differences in cation-anion, anion-π, and π-π interactions perturbed the metal-based HOMO and pyridyl π*-based LUMO levels. Changing the anion of 2 produces green-2ClO4, yellow-2ClO4, and 2PF6. These analogues further support the role of the anion in the luminescence modulation of 2. In Chapter 3, the luminescence modulation of a series of Cu4X4L2 clusters is explored. The Cu(I) halide clusters, Cu4Cl4(PPh2py)2 (4), Cu4Br4(PPh2py)2 (5), and Cu4I4(PPh2py)2 (6), were prepared by mixing PPh2py and the appropriate Cu(I) halide in dichloromethane/acetonitrile. The structural motifs of 4-6 vary as a function of the halide; the Cu4X4 cores of 4 and 5 are octahedral while the core of 6 is butterfly-shaped. Crystallization of 4-6 in various solvents also produces Cu4Cl4(PPh2py)2(NCCH3)2 (4a), Cu4Br4(PPh2py)2·2CH2Cl2 (5·2CH2Cl2), Cu4Br4(PPh2py)2·2CHCl3 (5·2CHCl3), (Cu2Br2PPh2py)n (5a), and Cu4I4(PPh2py)2·0.5CH2Cl2 (6·0.5CH2Cl2). Differences in Cu4X4 cores, halide bonding, and intermolecular interactions produce copper cluster emissions ranging from green to orange. Electronic structure calculations indicate that the lowest-energy triplet-singlet emission is a mixed metal- and halide-to-ligand charge transfer (M+X)LCT. The luminescence modulation of compounds 4-6 and its solvates highlight the effect of solvent processing on the emission of Cu(I) halide complexes for use in OLEDs (organic light-emitting diodes). In Chapter 4, the luminescent mechanochromism and thermochromism of a Au(I)-Cu(I) N-heterocyclic carbene (NHC) complex is reported. The Ag(I) species [Ag(benzim(CH2py)2]PF6 (7) is prepared by refluxing the ligand precursor [H(benzim(CH2py)2]PF6 and Ag2O with NaOH and the phase transfer catalyst Bu4NPF6 in dichloromethane. The Au(I) analogue [Au(benzim(CH2py)2]PF6 (8) is prepared by transmetallation of 7 with tetrahydrothiophenegold(I) chloride. Addition of [Cu(NCCH3)4]PF6 to 8 in acetonitrile produces the trimetallic complex [AuCu2(benzim(CH2py)2(NCCH3)4](PF6)3·2CH3CN (9·2CH3CN). Upon exposure to air, 9·2CH3CN loses four acetonitrile molecules to form 10. Recrystallization of 10 in various solvents produces structures of acetonitrile-free [AuCu2(benzim(CH2py)2](PF6)3 (11) and propionitrile-containing [AuCu2(benzim(CH2py)2(NCCH2CH2CH3)2](PF6)3 (12). Upon grinding, the emissions of blue-luminescent 9·2CH3CN and aqua-emissive 10 appear intense yellow. The conversion of 9·2CH3CN to ground-10 is a crystalline-to-amorphous transformation facilitated by loss of solvent and reversed by recrystallization. The mechanochromic conversion of 10 to ground-10 is an irreversible "amorphous to amorphous" transformation without loss of acetonitrile. Upon grinding, the anion environments of 10 are significantly perturbed as indicated by the 19F{1H} and 31P{1H} solid-state NMR (ssNMR) spectra of 10 and ground-10. In addition to their mechanochromic properties, 9·2CH3CN and 10 also exhibit irreversible thermochromic transformations to form weakly luminescent, acetonitrile-free 13. In Chapter 5, the reversible thermochromism of a two-coordinate Au(I)-Cu(I) phosphine complex is reported. The Au(I) complex [Au(Ph2PCH2py)2]BF4 (14) is produced from the mixture of tetrahydrothiophenegold(I) chloride and Ph2PCH2py with excess NaBF4 in dichloromethane. Addition of [Cu(NCCH3)4]BF4 to 14 in acetonitrile produces the Au-Cu complex [AuCu(Ph2PCH2py)2(NCCH3)2](BF4)2 (15). Upon exposure to air, crystals of green-luminescent 15 desolvate to form crystals of yellow-luminescent, acetonitrile-free [AuCu(Ph2PCH2py)2](BF4)2 (16). The dichloromethane solvate [AuCu(Ph2PCH2py)2](BF4)2·CH2Cl2 (16·CH2Cl2) was also characterized crystallographically. In the solid-state, the emission of 16 is intensely yellow at room temperature but changes as a function of temperature. The emission appears bright green at 77 K and aquamarine at 403 K but returns to yellow at 298 K. The blue-shift in emission upon cooling is attributed to luminescent rigidochromism. An endothermic phase change is responsible for the aqua emission of 16 at 403 K. However, the 19F{1H} and 31P{1H} ssNMR spectra do not indicate significant structural differences for 16 at 298 and 403 K. It is possible that a singlet harvesting mechanism through thermally-activated delayed fluorescence (TADF) is responsible for the blue-shift in emission at 403 K, but a structural rearrangement cannot be ruled out.
Description
Citation
Publisher
License
In Copyright(All Rights Reserved)