Synthesis and characterisation of $(EP_2)$M complexes (E = Si, Bi; M = Cu, Ni) and the study of their reactivity and photophysical properties

Abstract

In Chapter 1, a background on photoluminescent copper complexes and bismuth-metal compounds are discussed. In Chapter 2, the synthesis, characterisation and photophysical properties of ($Si^HP_2$)Cu($Cbz^R$) complexes are discussed. The $Si^HP_2$ ligand shows $\sigma$-complexation with the copper centre to give flattened-tetrahedral geometry with an anionic carbazolide ligand, which previously was shown to minimise geometry reorganisation on excitation. Halide substitution at the 3- and 6-positions of the carbazolide resulted in emission from a ligand-centred excited state. Alkyl and aryl substitution results in emission from a metal-to-ligand excited state. The electronic effect was able to give a large $\lambda_{max}$ range of 418 to 511 nm. Substitution at the 1-position resulted a tilting of the carbazolide moiety, while the geometry about the copper centre is unperturbed. The tilting affects the bonding between copper and nitrogen, reducing the highest-lying copper-based molecular orbital. In the case of the di(trifluoromethyl)carbazolide complex combined electronic and steric effects result in deep-blue emission with a $\lambda_{max}$ of 430 nm from a charge-transfer excited state. Chapter 3 details the synthesis and characterisation of nickel-bismuth complexes and their small molecule activation reactivity. Oxidative addition of a Bi-C bond by $Ni(0)(COD)_2$ affords a ($BiP_2$)Ni(II) complex with a covalent metal-metal bond. Oxidative addition of methyl iodide breaks the Ni-Bi bond to give the addition product. On heating or irradiating with UV light, the metrhyl iodide addition product undergoes reductive elimination to give ($BiP_2$)NiI, which possesses a $\tau_4$ value of 0.51. CO addition to ($BiP_2$)NiP results in a CO-bonded intermediate followed by migratory-insertion into the Ni-C bond to form a carbonyl product. Oxidative addition of methyl iodide and subsequent reductive elimination reactions occur faster with the carbonyl complexes. Chapter 4 discusses the synthesis and characterisation of bismuth-copper complexes. A $BiP_3$ ligand was metalalated with copper to give [($BiP_3$)Cu$(MeCN)_4$][$PF_6$]. When irradiated with UV light, Bi-C cleavage occurred, with subsequent Bi-Bi bond formation to give the dimer product. Reaction with chloroform gave ($BiP_2$)CuCl, which is photoluminescent in frozen toluene at 77 K.