Narrow Results

Equilibrium constants (1:1) for the reactions of cadmium(II) and lead(II) with water-soluble free base porphyrins of differing basicities (pK₃) are reported. Soft porphyrins with low pK₃ values favor the softer Cd(II), while harder porphyrins with higher pK₃ values have more affinity for the relatively harder Pb(II) ion.

We study the change in internal rotational energy in the transformation of protons to neutrons in the $\beta$-decay reactions that take place in the collapse of the iron core of massive stars that precede Type II supernova explosions. We consider an ensemble of electrons, protons, neutrons and neutrinos undergoing $\beta$-decay reactions, treat the protons and neutrons as triatomic rotors, evaluate the equilibrium constant to obtain the change in rotational energy during the proton-to-neutron transformation. We estimate such change for a variety of conditions, and compare with the energy released in a supernova explosion.

The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH₂Cl₂ for derivatives containing four $\beta$,${\beta }^{\prime }$-fused butano or benzo groups and the equilibrium constants (log$K)$ determined using spectral titration methods. The examined compounds are represented as butano(YPh)₄PorZn and benzo(YPh)₄PorZn, where Por is the porphyrin dianion and Y is a CH₃, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano- and benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH₂Cl₂ and this leads to a 4–22 nm red-shift of the Soret and Q bands. The log$K$ values range from 1.98 to 4.69 for butano(YPh)₄PorZn and from 3.42 to 5.36 for benzo(YPh)₄PorZn, with the exact value depending upon the meso and $\beta$-substituents of the porphyrin and the conjugate acid dissociation constants (p$K_a)$ of the nitrogenous base.

The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH₂Cl₂ for derivatives containing four β,β′-fused butano or benzo groups and the equilibrium constants (logK) determined using spectral titration methods. The examined compounds are represented as butano(YPh)₄PorZn and benzo(YPh)₄PorZn, where Por is the porphyrin dianion and Y is a CH₃, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano- and benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH₂Cl₂ and this leads to a 4–22 nm red-shift of the Soret and Q bands. The logK values range from 1.98 to 4.69 for butano(YPh)₄PorZn and from 3.42 to 5.36 for benzo(YPh)₄PorZn, with the exact value depending upon the meso and β-substituents of the porphyrin and the conjugate acid dissociation constants (pK_a) of the nitrogenous base.