Abstract
Photosensitive dyes often induce charge transfer (CT) between adjacent chemical species and themselves under irradiation of appropriate wavelengths. Because of the reversibility and selectivity of such CT, it is considered to be interesting to utilize such dyes as optically controllable trigger components for conduction and magnetism in the photoexcited states of organic materials. Based on this idea, such a type of new salts, i.e., γ- and δ-DiCC[Ni(dmit)2] in addition to DiCC2[Ni(dmit)2]3 have been prepared, characterized and their physical and structural properties have been examined both under dark and irradiated conditions (dmit2− = 1,3-dithiole-2-thione-4,5-dithiolate, DiCC+ = 3,3′-Dihexyloxacarbocyanine monocation). Among them, under UV (254–450 nm) irradiation, δ-DiCC[Ni(dmit)2] exhibited photoconductivity being six times as high as its dark conductivity at room temperature. The electron spin resonance (ESR) spectra have demonstrated that there are photoexcited spins on both DiCC and [Ni(dmit)2] species as a result of the CT transition between them, serving as localized spins (DiCC) and carriers ([Ni(dmit)2]), respectively. The results obtained in this work have indicated that the strategy mentioned above is effective in developing organic photoresponsive semiconductors with paramagnetism.
Highlights
Some kind of aromatic amines and bipyridyl derivatives have attracted attention in various research fields for a long time as photosensitive dyes, which exhibit strong reducing or oxidizing abilities under irradiation [1,2,3,4,5,6,7,8]
Irradiation of light with appropriate wavelengths would bring about charge transfer (CT) transition to produce unpaired electrons/holes on both of the dyes and the building blocks in a transient way
As long as the irradiation continues, the excitation and relaxation happen wavelengths would bring about CT transition to produce unpaired electrons/holes on both of the Mdaygensetaocnhdemtishtrey b20u1i7l,d3i,n2g0 blocks in a transient way
Summary
Some kind of aromatic amines and bipyridyl derivatives have attracted attention in various research fields for a long time as photosensitive dyes, which exhibit strong reducing or oxidizing abilities under irradiation [1,2,3,4,5,6,7,8]. The three salts were basically comprised of mixed-stacking structures or alternate arrangement of cations and anions like ionic crystals. RReedd;; NNii((ddmmiitt)) aannoonn,, bblluuee;; DDiiCCCC ccaattiioonn,, hhyyddrrooggeenn aattoommss aarree oommiitttteedd ffoorr ccllaarriittyy:: ((aa)) aassyymmmmeettrriicc uunniitt;; ((bb))vviieewwddoowwnnaalloonnggbb-‐aaxxiiss;; ((cc)) vviieeww ddoowwnn aalloonngg aa-‐aaxxiiss;; ((dd)) iinntteerraaccttiioonn bbeettwweeeenn aanniioonnss iinn tthhee bbcc‐-ppllaannee. RReedd;; NNii((ddmmiitt))22aannoonn,,bblluuee;;DDiiCCCC ccaattiioonn,, hhyyddrrooggeenn aattoommss aarree oommiitttteedd ffoorr ccllaarriittyy:: ((aa))aassyymmmmeettrriiccuunniitt;;((bb))nneeiigghhbboorriinnggccaattiioonnaarrrraannggeemmeenntt;; ((cc))vviieewwddoowwnn aalloonngg aa‐-aaxxiiss;; ((dd))iinntteerraaccttiioonn bbeettwweeeenn aanniioonnss iinn tthheebbcc‐-ppllaannee. The g-values of a part of the spins on the N atoms (#3 (N) in the dark conditon in Table A2 were markedly enhanced compared with those of isolated spins on the bipyridine derivatives (g ~2.00 for N atoms), indicating strong interaction with the spins having larger g-values such as those in heavy atoms and transition metals, i.e., indicating strong interaction between cations and anions This is consistent with the crystal structure. This indicates that the photoexcitation corresponds to the CT from the anions to the cations producing localized spins on the cations and doping holes in the anions’ bands at the same time
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