The synthesis of magnesium tetraarylporphyrins has been investigated using magnesium halides in noncoordinating solvents with hindered amine bases. The rate of reaction increases in the series MgCl2 « MgBr2 < MgBr2• 0(Et)2 < Mgl2. Considerable latitude exists in selecting among magnesium reagents (MgBr2, MgBr2-0(Et)2, Mgl2), solvents (toluene, CH2C12, CHCI3), and bases (triethylamine, diisopropylethylamine, 2,2,6,6-tetramethylpiperidine) for efficient metalation of tetraphenylporphyrin at room temperature. Thus treatment of a toluene, CH2C12, or CHCI3 solution of tetraphenylporphyrin with excess MgBr2, MgBr2O(Et)2, or Mgl2 and triethylamine at room temperature quantitatively affords the magnesium chelate in <10 min. Tetramesitylporphyrin is converted to the magnesium chelate with Mgl2 and diisopropylethylamine in CH2C12 at room temperature in 10 min or by reaction with MgBr2O(Et)2 and triethylamine in toluene at 60 °C for 1 h. [Tetrakis(2,6-dimethoxyphenyl(porphinato]magnesium(II) was formed in similar fashion. The reaction conditions are compatible with porphyrins bearing (trimethylsilyl)ethynyl groups, and the reactions can be performed in the presence of zinc tetraphenylporphyrin without transmetalation. This approach is fundamentally distinct from that with DMF-MgCl2, which is designed to achieve high mutual solubility of the metal ion and free base porphyrin at elevated temperature. The facile magnesium insertion achieved with MgBr2, MgBr20(Et)2, or Mgl2 at room temperature is attributed to the lability of their ligands, their partial organic solubility, and the limited stability of their crystal lattices relative to the porphyrin magnesium chelate. A noncoordinating milieu is essential to avoid forming octahedral complexes of magnesium that are more stable than the magnesium porphyrin. The ability to form magnesium tetraarylporphyrins under gentle conditions enables biomimetic studies where zinc porphyrins have previously been used.

A density functional theory (DFT) and atoms-in-molecules (AIM) analysis has been applied to the intramolecular hydrogen bonding in the enol conformers of malonaldehyde and its fluoro-, chloro-, cyano-, and nitro-substituted derivatives. With the B3LYP/6-311++G(2d,p) method, good agreement between the DFT geometries and published experimental structures has been found. The donor-acceptor distance was also varied in a series of constrained optimizations in order to determine if energetic, structural, and topological trends associated with intermolecular hydrogen bonding remain valid in the intramolecular case. At very short donor-acceptor distances (<2.24 A), the hydrogen is symmetrically located between donor and acceptor; at distances longer than this, the hydrogen bonding is no longer symmetric. The AIM methodology has been applied to explore the topology of the electron density in the intramolecular hydrogen bonds of the chosen model systems. Most AIM properties for intramolecular hydrogen bond distances longer than 2.24 A show smooth trends, consistent with intermolecular hydrogen bonds. Integrated AIM properties have also been used to explore the phenomenon of resonance-assisted hydrogen bonding (RAHB). It is shown that as the donor-acceptor distance is varied, pi-electron density is redistributed among the carbon atoms in the intramolecular hydrogen bond ring; however, contrary to prior studies, the integrated atomic charges on the donor-acceptor atoms were found to be insensitive to variation of hydrogen-bonding distance.

Salts of 12-alkyl and 12-phenyl derivatives of the CB11H12 - anion are prepared in 50−60% yields from the 12-iodo-CB11H11 - anion by Pd-catalyzed cross-coupling with Grignard reagents. The tropylium ylide 12-C7H6 +-CB11H11 - is made in 54% yield by reaction of C7H7 + with CB11H12 -. Its ground-state dipole moment is 11.25 ± 0.1 D and its first hyperpolarizability is β = 236 × 10-30 esu at 1064 nm, as determined by hyper-Rayleigh scattering measurement. This value is ten times that of p-nitroaniline and is surprisingly large considering that the compound is colorless.