[reaction: see text] Palladium porphyrins are valuable photosensitizers and luminescent agents in biology and materials chemistry. New methodology is described wherein a 1-acyldipyrromethane is converted into the palladium chelate of a trans-A(2)B(2) porphyrin via a one-flask reaction. The reaction entails self-condensation of the 1-acyldipyrromethane in refluxing ethanol containing KOH (5-10 mol equiv) and Pd(CH(3)CN)(2)Cl(2) (0.6 mol equiv) exposed to air. This direct route to palladium porphyrins is more expedient than the four steps of the traditional synthesis: (1) reduction of the 1-acyldipyrromethane; (2) acid-catalyzed condensation; (3) oxidation of the porphyrinogen intermediate; and (4) metal insertion. The new synthesis requires neither acid nor DDQ and formally entails only a 2e(-) + 2H(+) oxidation overall versus the traditional multistep synthesis which requires a 2e(-) + 2H(+) reduction per each 1-acyldipyrromethane (4e(-) + 4H(+) overall) followed by a 6e(-) + 6H(+) oxidation. The analogous reaction of a 1,9-diacyldipyrromethane and a dipyrromethane also gives the palladium porphyrin. Seven palladium porphyrins have been prepared in yields of 25-57%. The direct route also can be used with Cu(OAc)(2).H(2)O to give the copper porphyrin albeit in low yield. In summary, this methodology readily affords palladium porphyrins directly from acyldipyrromethanes.

The excited-state structural dynamics of nickel(II)tetrakis(2,4,6-trimethylphenyl)porphyrin (NiTMP) and nickel(II)tetrakis(tridec-7-yl)porphyrin (NiSWTP) in a toluene solution were investigated via ultrafast transient optical absorption spectroscopy. An ultrashort stimulated emission between 620 and 670 nm from the S1 state was observed in both nickel porphyrins only when this state was directly generated via Q-band excitation, whereas such a stimulated emission was absent under B (Soret)-band excitation. Because the stimulated emission in the spectral region occurs only from the S1 state, this photoexcitation-wavelength-dependent behavior of Ni(II) porphyrins is attributed to a faster intersystem crossing from the S2 state than the internal conversion S2 --> S1. The dynamics of the excited-state pathways involving the (pi, pi*) and (d, d) states varies with the meso-substituted peripheral groups, which is attributed to the nickel porphyrin macrocycle distortion from a planar configuration. Evidence for intramolecular vibrational relaxation within 2 ps and vibrational cooling in 6-20 ps of a (d, d) excited state has been established for NiTMP and NiSWTP. Finally, the lifetimes of the vibrationally relaxed (d, d) state also depend on the nature of the peripheral groups, decreasing from 200 ps for NiTMP to 100 ps for the bulkier NiSWTP.

To create potentially superior aids to smoking cessation and/or antidepressants and to elucidate bupropion’s possible mechanisms of action(s), several analogues based on its active hydroxymetabolite (2S,3S)-4a were synthesized and tested for their abilities to inhibit monoamine uptake and nAChR subtype activities in vitro and acute effects of nicotine in vivo. The 3′,4′-dichlorophenyl [(±)-4n], naphthyl (4r), and 3-chlorophenyl or 3-propyl analogues 4s and 4t, respectively, had higher inhibitory potency and/or absolute selectivity than (2S,3S)-4a for inhibition of DA, NE, or 5HT uptake. The 3′-fluorophenyl, 3′-bromophenyl, and 4-biphenyl analogues 4c, 4d, and 4l, respectively, had higher potency for antagonism of α4β2-nAChR than (2S,3S)-4a. Several analogues also had higher potency than (2S,3S)-4a as antagonists of nicotine-mediated antinociception in the tail-flick assay. The results suggest that compounds acting via some combination of DA, NE, or 5HT inhibition and/or antagonism of α4β2-nAChR can potentially be new pharmacotherapeutics for treatment of nicotine dependence.