Abstract
ABSTRACT This thesis reports on the synthesis of novel iridium complexes and the photophysical, electrochemical and electroluminescent studies based on them. The details are presented in three chapters. Chapter 2 explains the synthesis of alkenyl pyridine based iridium complexes. In Chapter 3, iridium complexes synthesized based on thiazoles and quinolines are discussed. In Chapter 4, complexes with unusual properties are discussed. Various alkenyl pyridines were synthesized by Stille coupling, Mizoroki-Heck reaction and Wittig reactions. The trans isomers were treated with IrCl3.nH2O to get the binuclear complexes. The binuclear complexes were then converted to emissive mono nuclear acetyl acetonate complexes by reported methods. Surprisingly cis or a mixture of cis and trans isomer was also found to undergo cyclometalation. These complexes exhibit red shifted emission compared to their aromatic analogues. The emission wavelength does not alter much when electron withdrawing or donating groups are substituted on the pyridine ring or the para position to the phenyl ring. Chapter 3 explains the detailed synthetic photoluminescent and electroluminescent studies of alkenyl pyridine based complexes. Various alkenyl thiazoles and alkenyl quinolines were synthesized by Stille coupling and Wittig reactions. They were conveniently converted to the corresponding metal complexes by following previous reported methods. A red shifted emission was observed for the alkenyl quinolines based iridium complexes. In Chapter 3, the details of the photophysical and electroluminescent properties of these complexes are explained. The devices based on (PEQ)2Ir(acac) as dopant showed excellent red emission with CIE values (0.66,0.33). Compounds discussed in Chapter 4 show abnormal photophysical and electroluminescent properties. These ligands were synthesized by Wittig reactions. The ligands were treated with IrCl3.nH2O and then with acetyl acetone to give final iridium complexes. These complexes are weakly luminescent or non luminescent in solution and extremely luminescent in solid state. They show good to excellent device properties when they were used as dopants in devices. The devices based on (MPP)2Ir(acac) and (PPP)2Ir(acac) showed excellent device performance when used as dopants. A detailed explanation about these compounds is discussed in Chapter 4. Newly designed ligands were synthesized to get efficient photoluminescent and electroluminescent iridium complexes. The complexes are highly luminescent in solid state. Chapter 4 also explains about the attempted synthesis of platinum complexes using these ligands. Two complexes (PEP)Pt(acac) and (PEQ)Pt(acac) were synthesized using ligands PEP and PEQ. These complexes are highly luminescent in solid state.