A novel porphyrin–BODIPY dyad, where BODIPY acts as the central antenna, linked via the Sonogashira coupling reaction, and a novel porphyrin–o-carborane–BODIPY triad, where both porphyrin and BODIPY are covalently attached to the o-carborane, have been synthesised and characterised. X-ray crystallography confirmed a V-shaped triad molecule. Detailed studies on the photophysical properties revealed the excitation of the BODIPY dyad system, which selectively triggered an efficient resonance energy transfer to the porphyrin unit. The presence of the o-carborane group in the triad system significantly diminished the energy transfer efficiency from BODIPY to the porphyrin moiety, because of its quenching properties. Besides, the triad system displayed aggregation-enhanced emission in THF/water systems, due to the presence of the o-carborane unit. The in-depth investigation of the electrochemical properties demonstrated that o-carborane insertion extended the initial reduction potentials and shifted half waves from the anodic to the cathodic site.
31 March 2009 in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Dielectric spectroscopy measurements of conductivity were applied for understanding the change in the internal morphology of the neutral and permanently charged polyacrylamide (PAAm) hydrogels during the swelling process. For the first time four distinct peaks (each corresponding to a different swelling stage) in the conductivity of the neutral gel were observed during the swelling of this gel. These peaks are related to the distribution of dense polymer regions (they are defined as the “blobs”) appearing in a microstructure of the given PAAm gel having at least four average sizes. For the charged gel the heterogeneity decreases due to the internal electric field of the charged sites. Thus, this characteristic behavior in the conductivity becomes almost negligible for the gel charged with permanent SO3− groups. It seems this fact causes considerable decrease in amplitude of the peaks and overall decrease the conductivity during the whole swelling process especially at high frequencies. The new theory of dielectric relaxation based on the fractional kinetics containing the complex power-law exponents was used for verifying these swelling processes and received an excellent confirmation in description of the real part of the complex conductivity Re[σ(ω)] by the fitting function that follows from the suggested theory. The calculated power-law exponents describe the behavior of Re[σ(ω,m∕m0)] in the available frequency range (30Hz–13MHz) and for all values of the relative masses (volumes) measured in the process of the experiment. The excellent coincidence between the new theory and measured data gives a possibility to suggest more reliable physical picture of the swelling process that takes place in neutral/charged gels.
1 August 2018 in Journal of Organometallic Chemistry