Electronic/substituents influence on imidazole ring donor–acceptor capacities using 1H-imidazo[4,5-f][1,10]phenanthroline frameworks

Abstract

Eight imidazole-based compounds 4-methyl-2,6-bis(4,5-diphenyl-1H-imidazol-2-yl)phenol (A-dp), 2-(1H-phenanthro[9,10-d]imidazol-2-yl)phenol (B-2H), 5-methoxy-2-(1H-phenanthro) were synthesized and characterized by elemental, spectroscopic and X-ray single crystal analyses. Two different crystals of A-dp were grown from ethanol and THF, which revealed that A-dp crystallizes in a monoclinic (P2(1)/c) space group while A-dpÁ2THF crystallizes in a triclinic (P % 1) space group. A-dpÁ2THF was devoid of any kind of networks whereas the absence of solvent adducts in the ethanol sample produces 1-dimensional single-stranded helices. Contrary to the reported literature conclusion that 1H-imidazole alkylation should increase the donor strength of the imidazole N-base, protonation-deprotonation equilibrium studies on the compounds suggest that push/pull of electron density on the 2-carbon of the imidazole ring by electron-rich/ electron-withdrawing substituents is necessary to influence donor capacity of the N-base electrons. Furthermore, the notable increase in pK a,N: values due to ortho/para-directing methoxy substituents supports the conclusion that electron density push towards the 2-position of the imidazole ring is important for improving N-base donor strengths. DFT calculation results using the B3LYP/6-311+G level of theory were conducted to explore possible theoretical explanations.

Efficient donor–acceptor emitter based nonsymmetrical connection for organic emitting diodes with improving exciton utilization

“…The h r calculated for p-PPI (49-56%), m-PPI (37-46%), p-CNPPI (41-52%) and m-CNPPI (37-46%) indicates g is less than 100% due to very small unbalanced carrier transportation. 64 This result could be attributed more balanced charge-transporting properties in the emissive zone achieved by better charge injection provided by hole transport layer. The h IQE can be calculated from h EQE O h out as 31% (p-PPI), 35% (m-PPI), 29% (p-CNPPI) and 34% (m-CNPPI) and maximum h s of 39% (p-PPI), 51% (m-PPI), 33% (p-CNPPI) and 46% (m-CNPPI) of EL devices is determined using the equation,…”

“…7). The lm quantum yield of p-PPI, m-PPI, p-CNPPI and m-CNPPI lms are of 80.0%, 70.0%, 86.0% and 73.0% respectively, thus the upper limit of h ex calculated from the following equation: [62][63][64] , [h outlightout-coupling efficiency (20%), h rcproduct of the charge recombination efficiency (100%), h gefficiency of radiative exciton production (25%) and F PLphotoluminescence quantum yield]. The h r calculated for p-PPI (49-56%), m-PPI (37-46%), p-CNPPI (41-52%) and m-CNPPI (37-46%) indicates g is less than 100% due to very small unbalanced carrier transportation.…”

Strategic tuning of excited-state properties of electroluminescent materials with enhanced hot exciton mixing

“…The h r calculated for DPIAPPB (40-50%) and CADPPI (29-36%) indicates g is less than 100% due to very small unbalanced carrier transportation. 77 1%) and CADPPI (42.9%) was breaking through the limit of 25% according to spin statistics, these two molecules exhibit light emitting mechanism as HLCT ( Fig. 3): 10.1% of triplet translate to singlet excitons by reverse intersystem crossing progress to enhance the uorescence emission and the rest lie away through non-radiative progress for DPIAPPB.…”

Cyclometallation, steric and electronic tendencies in a series of Pd(II) complex pre-catalysts bearing imidazole–phenol ligands and effects on Suzuki–Miyaura catalytic efficiencies

“…The compounds p-tBu~dm, pM~dm, p-N~dm, de, o-tBu~dp, dp, o-H~dp, o-M~dp, p-M~dp, p-Br~dp, p-N~dp, Naph~dp, m-M~pt, Bis-Im, Pd(p-N~dm) 2 and Pd(de) 2 were obtained according to recently reported procedures. 39,42,45,46 In order to exclude impurities, the organic compounds were either purified on silica gel columns or re-crystallized. Elemental analyses were performed on Leco CHNS-932 or El Vario III elemental analyzers.…”

“…In particular, oxazole moieties in these ligand families were observed to be poorer donors compared to imidazoles. [41][42][43][44][45] On the basis of knowledge derived from observed structural results of some members of the 2-(1H-imidazol-2-yl)phenol series 39,46 and donor strength studies 42,43,45,47 conducted for the ligand family, it was anticipated that a relatively wide variations in coordination / chelation preference would exist for palladium complexes of the 2-(1H-imidazol-2-yl)phenols. Furthermore, it was anticipated that, with systematic variation on ligand electronic, steric and chelation characters, some information about the configuration of active palladium species would be learned.…”