Tetraazachlorin−Fullerene Conjugates:  On−Off Control of Electronic Communication Enabled by Push−Pull Substituents

Abstract

Novel tetraazachlorin (TAC)-fullerene (C60) conjugates (TAC-C60) and their analogues (TAiBC-C60 and TABC-C60 where TAiBC ) tetraazaisobacteriochlorin and TABC ) tetraazabacteriochlorin) have been synthesized by condensing 1,2-dicyanofullerene (1) and phthalonitrile derivatives (2) in the presence of nickel chloride in quinoline, and fully characterized using mass spectrometry and 1 H and 13 C NMR. By arranging the TAC and C60 units at the minimum distance, and taking also into account the molecular symmetry, the resultant conjugates show on-off electronic communication behavior, depending on the push-pull properties of the peripheral substituents in the TAC moiety. Consequently, the UV-vis absorption spectrum of the electron-releasing butyloxy-substituted TAC-C60 (3a) contains an unusual group of three absorption bands in the Q-band region (500-900 nm) as a result of a strong electronic communication between the two moieties. On the other hand, the absorption spectrum of the electron-withdrawing butylsulfonyl-substituted TAC-C60 (3b) comprises a typically normal TAC spectrum with markedly split two-peak Q-bands. A similar phenomenon is observed between alkoxy-substituted TAiBC-C60 (4a) and butylsulfonyl-substituted TAiBC-C60 (4b). This study reveals that the electron-donating or -withdrawing nature of the peripheral substituents on an azachlorin moiety has an important effect on the electronic structures of our novel azachlorin-C 60 conjugates, although the linking carbon atoms are aliphatic sp 3 carbon atoms which generally do not contribute to aromaticity. The electronic structures of the conjugates have been investigated in detail using spectroscopic and electrochemical techniques with the aid of DFT calculations.

Linear and nonlinear optical properties of triphenylamine-functionalized C60: insights from theory and experiment

“…On the contrary, toluene was found to exhibit significant refractive nonlinearity under the experimental conditions used, as it is clearly shown in the divided Z-scans of neat toluene which exhibit a valley-peak configuration indicative of a focusing behavior (i.e. positive Rew (3) ) in agreement with other works. 36 Some representative divided Z-scan traces of the derivatives 1, 3 and toluene measured under identical experimental conditions are shown in Fig.…”

“…From the open-aperture Z-scan the nonlinear absorption b of the sample is determined, while from the division of the closed-aperture Z-scan trace by the open-aperture Z-scan trace, the so called divided Z-scan is obtained, which allows for the determination of the nonlinear refraction parameter g 0 of the sample. The former quantity is related to the imaginary part of the third-order susceptibility (Imw (3) ), while the latter is related to the real part of the third-order susceptibility. The openaperture Z-scan trace may exhibit a transmittance valley or peak near the focal plane indicative of positive or negative imaginary part of the third-order nonlinearity, respectively.…”

Design and synthesis of tetraazachlorins, tetraazabacteriochlorins and tetraazaisobacteriochlorins

“…Thus, these compounds were transformed into 2,3-substituted TBTAP (61, 62) as a result of an intramolecular rearrangement, with the migration of one of phenyl or methyl group to a neighboring carbon atom when the reaction time was increased and/or during chromatography on silica or alumina. Another example of reduced TAP analogs was reported recently by Fukuda et al [27,28]. Novel TBTAC-(66-68), DBTAiBC-(69, 70) and DBTABC-fullerene (C 60 ) (71) conjugates were synthesized by using 1,2-dicyanofullerene (63) as a source of hydrogenated sites in a mixed condensation with 4,5-dibutylsulfonyl-(64) or 4,5-dibutoxyphthalonitrile (65) in a 1:2 molar ratio in the presence of a metal salt (NiCl 2 or VCl 3 ) at 190 °C in quinoline (Scheme 12).…”

“…Recent advances in other approaches, namely the mixed condensation of the precursors with different hydrogenation levels, and β-β addition reactions have led to the synthesis of novel tetraazachlorins and previously unknown tetraazabacteriochlorins and tetraazaisobacteriochlorins, with a strong absorption in the red and near-infrared region of the spectrum. The progress in the synthesis of the new original structures has allowed the elucidation of their spectral, photophysical, electrochemical properties [20,21,27,28,34,[39][40][41][42][43]47] and persistent spectral hole burning [44], which were not considered in this review. Besides the signifi cant theoretical interest, these compounds are currently attracting considerable attention as a new class of effective photosensitizers [46] and non-linear optics materials [45].…”

Phthalocyanine, Porphyrin, Cyclodextrin, and Polymer Systems Suitable for Studying by Circular Dichroism, Magnetic Circular Dichroism, and/or Electrochemistry

“…41 From the reaction mixture, TAC with one fullerene 49 and 50, TAiB 51 and 52, and TAB 53 with two fullerene molecules were separated (Scheme 5). In order to extract the role of the fullerene unit, the corresponding compounds without fullerene units were also prepared similarly (Scheme 5).…”