Electrochemistry of a series of symmetric and asymmetric CpNiBr(NHC) complexes: Probing the electrochemical environment due to push-pull effects

2020

Inorg. Chem.

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Four new ferrocenylsubphthalocyanines Y-BSubPc, with ferrocenylcarboxylic acid YH = Fc-CH 2 −CH 2 −COOH (1) or Fc-CHCH−COOH (2) in the axial Y position, were synthesized with a 40% yield. The axial ferrocenylcarboxylic acid moiety did not have a significant influence on the position of the Q bands maxima of the UV/vis spectra of the ferrocenylsubphthalocyanines or on the 1 H NMR position of the ring proton peaks of Y-BSubPc(H 12 ) or on the 19 F NMR position of the ring F peaks of YSubPc(F 12 ), relative to their respective parent compounds Cl-BSubPc(H 12 ) 3 and Cl-BSubPc(F 12 ) 4, containing axial chlorine. Very weak metal-to-ligand-charge-transfer bands (MLCT) in the near-IR region were observed. An electrochemical study utilizing cyclic voltammetry showed that electronic communication exists between ferrocene on the axial ferrocenylcarboxylic acid and the π-electrons of the macrocycle of the ferrocenylsubphthalocyanine (Fc(CH 2 ) 2 COO)-BSubPc(H) 12 ,5, (Fc(CH) 2 COO)-BSubPc(H) 12 , 6, (Fc(CH 2 ) 2 COO)-BSubPc(F) 12 , 7, and (Fc(CH) 2 COO)-BSubPc(F) 12 , 8. The Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second oxidation localized on the subphthalocyanine ligand. The fluorine ring substituents in SubPcs 7 and 8 caused the ferrocenyl oxidation to shift more positive by ca. 0.1 V, compared to SubPcs 5 and 6 without fluorine. Density functional theory (DFT) calculations provided further insight into the properties of these novel ferrocenylsubphthalocyanines. The neutral species of SubPcs 5−8 have LUMOs with mainly π-ring character and HOMOs with mainly iron-d character, confirming ring-based reduction, metal-based Fe(II) to Fe(III) oxidation, as well as weak MLCT in the near-IR region. Further DFT optimization of the cation (oxidized) species was essential to verify the second ring-based oxidation.

Section: Resultsmentioning

confidence: 99%

Redox and Photophysical Properties of Four Subphthalocyanines Containing Ferrocenylcarboxylic Acid as Axial Ligands

Swarts

2020

Inorg. Chem.

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“…Upon reduction of mer molecule 1, an electron is added to the LUMO of complex 1, which is of

d_{x^{2} - y^{2}}

character (Figure 3). This LUMO then becomes the HOMO of the reduced molecule 1, if no re‐arrangement of the frontier orbitals occurs during reduction [31–33]. This new HOMO of the reduced mer complex 1, also shown in Figure 3, now has

d_{x^{2} - y^{2}}

character, while the new LUMO of reduced complex 1, as well as LUMO+1 to LUMO+10, is ligand based.…”

Section: Resultsmentioning

confidence: 89%

“…This was nicely illustrated by the occupied molecular orbital of (Figure 3). This LUMO then becomes the HOMO of the [31][32][33]. This new HOMO of the reduced mer complex 1, also shown in Figure 3, now has d x 2 À y 2 character, while the new LUMO of reduced complex 1, as well as LUMO + 1 to LUMO + 10, is ligand based.…”

Section: Dft Optimized Geometry and Properties Of Moleculesmentioning

confidence: 82%

Cyclic Voltammetric and DFT Analysis of the Reduction of Manganese(III) Complexes with 2‐Hydroxybenzophenones

Adeniyi

2020

Electroanalysis

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A comprehensive understanding of the redox behaviour of manganese complexes is significant for its use in different industrial applications, including as redox mediator in dye sensitized solar cells. This study presents the experimental reduction potential of derivatives of manganese(III) complexes coordinated to 2-hydroxybenzophenones, showing that the first observed experimental reduction potential peak is located on the manganese atom, followed by a further ligand-based reduction. A density functional theory study shows that Jahn-Teller distortion has a larger impact on the theoretically determined reduction potential and molecular electrostatic potential at the manganese atom, than the impact of the isomeric forms (fac and mer) on the theoretically predicted reduction potential. Keywords: 2-Hydroxybenzophenone • manganese(III) • reduction • DFT Highlights * First reduction of manganese tris(2-hydroxybenzophenone) complexes is Mn based * Second reduction of manganese tris(2-hydroxybenzophenone) complexes is ligand-based * Influence of Jahn-Teller effect on the theoretically determined reduction potential * Influence fac and mer isomers on the theoretically determined reduction potential * Experimental and theoretical Mn(III/II) reduction of manganese tris(2-hydroxybenzophenone) [a] A

“…However, since the top three highest occupied MOs (HOMOs) of 7-11 are all iron-d based, and Fe(III) to Fe(IV) oxidation is not expected, it was essential to also optimise the cation (oxidised) species, to locate the locus of the second experimentally observed oxidation. It is known that orbitals can rearrange upon oxidation [29][30][31]. The DFT results of oxidised SubPcs 7-11 all showed that the LUMO is of iron-d character (the first oxidation, see Figure 5) and the HOMO is on the SubPc ring (the second oxidation, see Figure 5).…”

Section: Computational Analysismentioning

confidence: 99%

Synthesis, Spectroscopy, Electrochemistry and DFT of Electron-Rich Ferrocenylsubphthalocyanines

Swarts

2020

Molecules

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A series of novel ferrocenylsubphthalocyanine dyads Y-BSubPc(H)12 with ferrocenyl-carboxylic acids Y-H = (FcCH2CO2-H), (Fc(CH2)3CO2-H) or (FcCO(CH2)2CO2-H) in the axial position were synthesized from the parent Cl-BSubPc(H)12 via an activated triflate-SubPc intermediate. UV/Vis data revealed that the axial ferrocenyl-containing ligand did not influence the Q-band maxima compared to Cl-BSubPc(H)12. A combined electrochemical and density functional theory (DFT) study showed that Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second oxidation localized on the macrocycle of the subphthalocyanine. Both observed reductions were ring-based. It was found that the novel Fc(CH2)3CO2BSubPc(H)12 exhibited the lowest first macrocycle-based reduction potential (−1.871 V vs. Fc/Fc+) reported for SubPcs till date. The oxidation and reduction values of Fc(CH2)nCO2BSubPc(H)12 (n = 0–3), FcCO(CH2)2CO2BSubPc(H)12, and Cl-BSubPc(H)12 illustrated the electronic influence of the carboxyl group, the different alkyl chains and the ferrocenyl group in the axial ligand on the ring-based oxidation and reduction values of the SubPcs.