$${\varvec{\pi }}$$-systems of symmetrizable Kac–Moody algebras

The structural and energetic properties of polyfluorene and its derivatives were investigated, using quantum chemical calculations. Conformational analysis of bifluorene was performed by using ab initio (HF/6-31G* and MP2/6-31G*) and density functional theory (B3LYP/6-31G*) calculations. The results showed that the local energy minimum of bifluorene lies between the coplanar and perpendicular conformation, and the B3LYP/6-31G* calculations led to the overestimation of the stability of the planar pi systems. The HOMO-LUMO energy differences of fluorene oligomers and its derivatives — 9,9-dihexylfluorene (DHPF), 9,9-dioctylfluorene (PFO), and bis(2-ethylhexyl)fluorene (BEHPF) — were calculated at the B3LYP/6-31G* level. Energy gaps and effective conjugation lengths of the corresponding polymers were obtained by extrapolating HOMO-LUMO energy differences and the lowest excitation energies to infinite chain length. The lowest excitation energies and the maximum absorption wavelength of polyfluorene were also performed, employing the time-dependent density functional theory (TDDFT) and ZINDO methods. The extrapolations, based on TDDFT and ZINDO calculations, agree well with experimental results. These theoretical methods can be useful for the design of new polymeric structures with a reducing energy gap.

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Design and evaluation of conjugated bridging .pi. systems. Molecular orbital characterization and electrochemical determination of the pentacarbonyltungsten binding site in two new ambidentate ligands

Inorganic Chemistry ◽

10.1021/ic00335a027 ◽

1990 ◽

Vol 29 (10) ◽

pp. 1898-1902 ◽

Cited By ~ 17

Author(s):

Wolfgang Kaim ◽

Stephen Kohlmann

Keyword(s):

Binding Site ◽

Molecular Orbital ◽

Electrochemical Determination ◽

Pi Systems

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An Effective Synthesis of N,N-Diphenyl Carbazolium Salts

Synlett ◽

10.1055/s-0036-1591848 ◽

2017 ◽

Vol 29 (10) ◽

pp. 1314-1318 ◽

Cited By ~ 8

Author(s):

Charles Diesendruck ◽

Sinai Aharonovich ◽

Nansi Gjineci ◽

Dario Dekel

Keyword(s):

Positive Charge ◽

Quaternary Ammonium Salts ◽

Simple Approach ◽

Ammonium Salts ◽

State Structure ◽

Pi Systems ◽

Effective Synthesis ◽

Short Time ◽

First Time ◽

General Method

Tetraaryl ammonium salts are a synthetic challenge, since there is no general method for the arylation of triaryl amines. Contrary to other quaternary ammonium salts, tetraaryl ammonium salts should be very chemically stable. The ipso carbons are not very electrophilic, since the positive charge is distributed throughout the pi systems and they have no acidic β hydrogens. Here we demonstrate a simple approach to N,N-diphenyl carbazolium salts using only three synthetic steps, allowing for an easy production of these salts in large amounts and in a relatively short time. In addition, we study the Cu(I) catalyzed multi-arylation of 2,2’-diaminobiphenyl, focusing on the regioselectivity of each step. Finally, we characterize, for the first time, the solid state structure of a tetraaryl ammonium salt.

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