Electrode reduction mechanism of aromatic nitriles in aprotic solvents

Romanin, Annamaria; Gennaro, Armando; Vianello, E.

doi:10.1016/s0022-0728(78)80265-4

Cited by 19 publications

(3 citation statements)

References 21 publications

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“…This is due to the reduction potentials of these substituents being more negative than those of nitro group. As shown in Figure 6, the half-wave reduction potentials of styrene (−2.41 V), 47 benzamide (−2.23 V), 48 benzonitrile (−2.03 V), 49 and benzaldehyde (−1.34 V) 50 are more negative than those of nitrobenzene (0.16 V). 42 This thus enables chemoselective nitro hydrogenation on the photoactivated rutile TiO 2 .…”

Section: ■ Results and Discussionmentioning

confidence: 95%

Highly Efficient and Selective Hydrogenation of Nitroaromatics on Photoactivated Rutile Titanium Dioxide

et al. 2012

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We report that photoactivated rutile titanium dioxide (TiO 2 ) catalyzes a highly efficient and selective hydrogenation of nitroaromatics with alcohol as a hydrogen source. Photoirradiation (λ >300 nm) of rutile TiO 2 suspended in alcohol containing nitroaromatics at room temperature and atmospheric pressure produces the corresponding anilines with almost quantitative yields, whereas common anatase and P25 TiO 2 show poor activity and selectivity. The Ti 3+ atoms located at the oxygen vacancies on the rutile surface behave as the adsorption site for nitroaromatics and the trapping site for photoformed conduction band electrons. These effects facilitate rapid and selective nitro-toamine hydrogenation of the adsorbed nitroaromatics by the surface-trapped electrons, enabling aniline formation with significantly high quantum yields (>25% at <370 nm). The rutile TiO 2 system also facilitates chemoselective hydrogenation of nitroaromatics with reducible substituents; several kinds of functionalized anilines are successfully produced with >94% yields.

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Section: ■ Results and Discussionmentioning

confidence: 95%

Highly Efficient and Selective Hydrogenation of Nitroaromatics on Photoactivated Rutile Titanium Dioxide

et al. 2012

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“…This difference is reflected by the reduction potential of nitrobenzene (À 0.58 V vs. SCE) [67] compared to that of benzonitrile (À 2.2 V vs SCE). [68] If the reduction potential of benzene (À 3.4 vs SCE) [69] is also considered, one can see that the difference of reduction potentials of the A and A' groups is larger for 4 (1.6 V) than for 1 (1.2 V). As a consequence, the charge-transfer character of the dipolar symmetry-broken S 1 state can be expected to be stronger for 4 than for 1.…”

Section: Swapping a And A'mentioning

confidence: 99%

Change of Quadrupole Moment upon Excitation and Symmetry Breaking in Multibranched Donor‐Acceptor Dyes

et al. 2020

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Upon photoexcitation, a majority of quadrupolar dyes, developed for large two‐photon absorption, undergo excited‐state symmetry breaking (ES‐SB) and behave as dipolar molecules. We investigate how the change of quadrupole moment upon S1←S0 excitation, ΔQ, influences the propensity of a dye to undergo ES‐SB using a series of molecules with a A‐π‐D‐π‐A motif where D is the exceptionally electron‐rich pyrrolo[3,2‐b]pyrrole and A are accepting groups. Tuning of ΔQ is achieved by appending a secondary acceptor group, A’, on both sides of the D core and ES‐SB is monitored using a combination of time‐resolved IR and broadband fluorescence spectroscopy. The results reveal a clear correlation between ΔQ and the tendency to undergo ES‐SB. When A is a stronger acceptor than A’, ES‐SB occurs already in non‐dipolar but quadrupolar solvents. When A and A’ are identical, ES‐SB is only partial even in highly dipolar solvents. When A is a weaker acceptor than A’, the orientation of ΔQ changes, ES‐SB is observed in dipolar solvents only and involves major redistribution of the excitation over the D‐π‐A and D‐A’ branches of the dye.

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“…The fourth irreversible reduction, shown in Figure b, is coupled to a rapid chemical reaction following electron transfer and appears to involve the loss of CN – from quadruply reduced MTPP(VCN) 2 . This process was not investigated in the current study where the primary emphasis is on synthesis and electrosynthesis of new π-extended porphyrins, but it should be noted that the reduction of cyanobenzene (benzonitrile) in DMF is located at ∼ −2.3 V vs SCE and involves a two-electron transfer followed by reductive decyanation. , The fact that the same potential is measured for the fourth reduction of MTPP(VCN) 2 in THF would indicate an electron transfer highly localized on one or both fused cyanobenzene rings.…”

Section: Resultsmentioning

confidence: 90%

Facile Heterogeneous and Homogeneous Anion Induced Electrosynthesis: An Efficient Method for Obtaining π-Extended Porphyrins

et al. 2020

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Two closely related electrosynthetic approaches are applied for the preparation of novel π-extended tetraphenylporphyrins from malononitrile-appended meso-β di-fused porphyrins, represented as MTPP(MN) 2 , where TPP = the dianion of tetraphenylporphyrin and MN = malononitrile. The first method involves application of a controlled reducing potential at a platinum electrode in CH 2 Cl 2 , while the second proceeds via cyanide anion induced electron transfer. Both methods produced the same decyanated, π-extended di-fused porphyrins represented as MTPP(VCN) 2 where VCN = vinyl cyanide and M = H 2 , Ni II , Cu II , or Zn II in almost quantitative yields. The final isolated and purified porphyrin products are characterized by a split Soret band ranging from 411−497 nm and two broad intense Q bands. The new π-extended porphyrins are easier to reduce than the parent MTPP or MTPP(MN) 2 compounds by 760−800 mV and 180−190 mV, respectively, and possess an electrochemical HOMO− LUMO gap ranging from 1.48 to 1.66 V. They are also characterized by two reversible one-electron ring-centered reductions in CH 2 Cl 2 and three reversible one-electron ring-centered reductions in THF. A fourth irreversible reduction is seen in THF at more negative potentials and is assigned to one or two of the fused cyanobenzene rings of the macrocycle.

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Electrode reduction mechanism of aromatic nitriles in aprotic solvents

Cited by 19 publications

References 21 publications

Highly Efficient and Selective Hydrogenation of Nitroaromatics on Photoactivated Rutile Titanium Dioxide

Highly Efficient and Selective Hydrogenation of Nitroaromatics on Photoactivated Rutile Titanium Dioxide

Change of Quadrupole Moment upon Excitation and Symmetry Breaking in Multibranched Donor‐Acceptor Dyes

Facile Heterogeneous and Homogeneous Anion Induced Electrosynthesis: An Efficient Method for Obtaining π-Extended Porphyrins

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