Cyclic Voltammetric Study of 3,5-Diaryl-1-phenyl-2-pyrazolines

Abstract

Cyclic voltammetry is used to derive HOMO energies of the 1phenyl-2-pyrazolines containing electron-donating or electron-withdrawing substituted phenyl rings and or naphthalenyl substitution on the C 3 -or C 5positions of the heterocyclic ring to investigate the steric and electronic effects of the aryl substitutions and the type of aryl system on their electrochemical behaviors. The optical HOMO−LUMO gaps needed for the calculation of LUMO (excited state) energies of these compounds are obtained from their UV−vis spectra. Results show that the substitution on the C 3 -aryl ring has significant effect via its π-donor/acceptor ability, compared to the σ-donor/ acceptor ability of the C 5 -aryl ring, on the CV oxidation peak and onset potentials. Comparative analysis showed very good agreement between the experimentally obtained HOMO and (apparent) LUMO energies and the (TD)DFT/6-311++G(d,p) calculated ground and excited states energies. These computational results indicate also that for all chloro-and methoxysubstituted 2-pyrazolines, the HOMO → LUMO is the most intense transition. While the strong acceptor NO 2 substitution on all positions of either C 3 -or C 5 -aryl rings, except for one compound, increases the intensity of the HOMO → LUMO+1 (LUMO+2) transition significantly, the first (the first two) transition(s) HOMO → LUMO (and HOMO → LUMO+1) has (have) much smaller or negligible intensity (intensities).

The development of a novel bio-based corrosion inhibitor: using biomass-derived 5-hydroxymethylfurfural (5-HMF) as a starting material

“…Calculation of HOMO and LUMO energy levels is carried out according to the oxidation potential and reduction potential presented in Fig. S10† by using the following equations: 23,24 E HOMO = − E ox + E 1/2 (Fc/Fc + ) − IP(Fc) E LUMO = − E red + E 1/2 (Fc/Fc + ) − IP(Fc)where E ox is the oxidation onset, E red is the reduction onset and E 1/2 (Fc/Fc + ) is the half-wave potential of ferrocene (0.0555 V). The energy value of the Fc/Fc + redox system is assumed to be IP(Fc) = 4.8 eV below the vacuum level.…”

A highly selective A–π–A “turn-on” fluorescent probe for hypochlorite in tap water

“…S6, ESI †), with ferrocene (Fc/Fc + ) as an internal standard electrode. [41][42][43] The HOMO energy levels of À5.766 and À5.906 eV, and the LUMO energy levels of À3.027 and À3.006 eV were estimated for BON and BODIPY-CHO, respectively (Table S2, ESI †). The electrochemical energy band gaps for BON and BODIPY-CHO were calculated to be 2.739 and 2.927 eV, respectively, and were basically consistent with the quantitative calculated results of 2.600 and 2.982 eV shown in Fig.…”

Spectroscopic Behaviour of Copper(II) Complexes Containing 2-Hydroxyphenones

“…Similarly, the theoretically calculated energy gap depends on the DFT method used. When calculating the theoretical energy gap, the specific Mos involved in the theoretical transition (e.g., at 401.2 nm for (5)), which agree with the experimental UV-Vis peak (401 nm for (5)), need to be used [30]; namely 37.7% HOMO-1 to LUMO + 3 (E gap = 3.68 eV) and 36.4% HOMO to LUMO + 4 (E gap = 3.67 eV) transitions for (5) (see Figure 4). The average of the E gap of the main transitions involved in theoretically calculated peak (∆E calc, A-max ), relates to the experimentally calculated E gap of the same peak (∆E exp, A-max ) for molecules (1)- (7), as well as to the excitation energy of the λ A,max peak (see Figure 10, data in Table 5).…”