Syntheses and Electronic Properties of the Nickel and Palladium Complexes of the Octaethylporphyrin(M1)-(Dihexylbithiophene)_n-Octaethylporphyrin(M2) System [OEP(M1)-(DHBTh)_n-OEP(M2)] Connected with the Diacetylene Linkage. A Methodology for Molecular De

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The synthetic methods for both symmetrical and unsymmetrical complexes of the OEP(M)-DHBTh-OEP(M) system have been conclusively described. Particularly, it is notable that the synthetic success of the terminal acetylenes 42 and 51 would lead to a general synthetic method for a variety of the OEP(M)-DHBTh-(π-EC) derivatives and would impel the present research onto the further application stage. ^1H NMR spectral study makes it confirmed that all the OEP(M)-(DHBTh)_n-OEP(M) derivatives possess the fairly simple skeletal features, regardless of the symmetry of molecule, with the respective ring currents of OEP(M) in 36 and 37 remaining to a great extent. And thus, the deshielded area from anisotropic effect of OEP(M) has proven to expand up to 25Å for the Ni complexes and 30Åfor the Pd complexes, reflecting the magnitudes of their ring currents (Fig.3). From the IR spectral measurements, it is derived that the diacetylene linkage for the TT series exhibits a greater contribution to an ext … More ension of the resonance structure with the OEP and DHBTh nuclei, regardless of the number of DHBTh. As contrasted with such a simple regularity in a rigid and straight molecular skeleton, the present π-electronic conjugation system possess characteristic absorption spectral features, reflecting several structure elements. The appearances of Soret and Q bands are peculiar to the present one-dimensionally extended π-electronic conjugation system, which exactly reflect the orientation of DHBTh. Absorption spectra for the HH,HT and TT isomers 1-3 show the respective Soret bands to split into two mainπ→π* transitions regularly, among which all the shorter wavelength λ_1 bands appear at around 440nm. The longer wavelength λ_2 bands, however, appear at the longer wavelength region separately over a range of 45nm. In both HH and TT series, the spectra of the Pd complexes 4 and 5 exhibit slight hypsochromic shift and sharpened, as compared with those for the corresponding Ni complexes 1 and 3. It is also proved that the introduction of (DHBTh)_n into 36 and 37 to form OEP(M)-(DHBTh)_n-OEP(M) (8-25) induces the gradual reformation between the two main electronic structures, reflecting both the orientation and n of DHBTh. With increases of n, the HH series the combined electronic system between OEP(M)-HTh and HTh-HH(DHBTh)_<n-2>-HTh, while the TT series does the conjugation system between OEP(M)-TT(DHBTh) and TT(DHBTh) _<n-2> (Fig.10). The solvent-dependent spectra of the OEP(Ni)-TT(DHBTh)-OEP(Pd) derivative 7 have been remarkably observed, though the transition origins of the sensitive bands to the solvent polarity must be further clarified. Concurrently with the orientation of DHBTh, the unsymmetrization by introducing the different OEP(M) rings into the present system is also potentially effective to conduct the electron transfer functionality from one side to the other.In consequence, the electronic absorption spectra of the OEP(M1)-(DHBTh)_n-OEP(M2) system could be affected substantially by the following structure elements. Putting those structure elements together from the material viewpoint, the orientation of DHBTh could be regarded as a function selector to construct the main electronic structure of the system, the incorporated metal ions M as a modulation tool for adjustment of the transition energy for each function band and the number of DHBTh as a fine tuner to select the susceptibility to the external electronic stimulations. Therefore, a particular electronic structure of OEP(M1)-(DHBTh)_n-OEP(M2) corresponding to the particular electronic property would be constructed by choosing these three structure elements purposively. Since the structure elements could be generalized to expand into the orientations of DABTh, many other metal ions and the greater numbers of n, respectively, the present study would provide a methodology for construction of the particular electronic structures of various DABTh derivatives at the stage of molecular design. Less