Solvent-polarity-tunable dimeric association of a fullerene (C60)-N,N-dimethylaminoazobenzene dyad: modulated electronic coupling of the azo chromophore with a substituted 3D fullerene.

摘要: The tunable self-assembly of a fullerene (C(60))-N,N-dimethylaminoazobenzene (DPNME) molecular system as function solvent polarity in THF/water binary is reported. Gradual increase the volume fraction nonsolvent water 1×10(-5) M THF solution DPNME at mixed dielectric constant e(mix)≈42 resulted initial redshifting (1)(π→π(*)) absorption band, which signified 1D head-to-tail or J-type arrangement system. Further to e(mix)≈66 evidenced formation an antiparallel H-type conjunction with J-aggregates, thereby establishing solvent-polarity-dependent dynamic equilibrium between monomer ↔ J-aggregate H-aggregate. controlled aggregation was governed by synergetic effect intermolecular donor-acceptor interaction electron-deficient ring and electron-rich N,N-dimethylamino-substituted aromatic ring; typically, van der Waals π-π interactions molecules constituting pair dimers were envisaged. An agreement semiempirically calculated drastically reduced oscillator strength H-dimer configuration (0.69 vs. 1.29 monomeric DPNME) experimental electronic spectra beyond e(mix)=66 further strengthened this assignment hitherto forbidden H-dimer. Complementing above, periodicity dictated monoclinic unit cell single-crystal XRD packing pattern C2/c space group; packed laterally mutual interdigitation donor (E)-N,N-dimethyl-4-(p-tolyldiazenyl)aniline (AZNME) parts fashion (contrary usual expectation for H-aggregates) strong inter- intrapair constituent moieties. Unlike those porphyrin/phthalocyanine bowl-like donor-initiated architectures, rare class dyadic supramolecular self-assemblies realized π-extended 2D networks, linear geometry AZNME conformational rigidity acceptor played crucial roles.