Pd(II), Ni(II), and Cu(II) complexes of α,α'-ditolylmethanone dipyrroethene.

Dipyrromethenes containing two pyrrole rings connected by one -carbon are versatile monoanionic bidentate ligands and form coordination complexes with many metals/nonmetals/metalloids. Dipyrroethenes containing one additional -carbon compared to dipyrromethenes have more space between coordinating pyrrole nitrogens and provide a good coordination environment but have not been explored as ligands in coordination chemistry. Dipyrroethenes are dianionic bidentate ligands and by suitable modifications, the coordination environment of dipyrroethenes can be changed further.

Piperazine Bridged Thianorrole Dimer.

Oxidative cyclization of open chain thiabilanes yielded the first examples of unique piperazine bridged thianorrole dimers instead of the expected thianorrole monomer. In the thianorrole dimer, the two thianorrole monomeric units are linked via two direct pyrrole C-C bonds by involving the inverted pyrrole and adjacent pyrrole rings of each thianorrole macrocycle and generate a six-membered piperazine ring that bridges the two thianorrole macrocycles. The spectral studies indicated that the thianorrole dimers are nonaromatic in nature.

Synthesis, Structure and Studies of Meso-Triaryl 22-Oxabenzonorroles.

The first examples of meso-triaryl 22-oxabenzonorroles were synthesized in 18-21% yields by oxidation of appropriate meso-triaryl oxabenzobilane. The key precursors, the meso-triaryl oxabenzobilanes were synthesized readily by treating 16-oxatripyrrane with (1H-indol-3-yl)(p-tolyl)methanol under acid catalyzed conditions. The meso-triaryl 22-oxabenzonorroles were obtained in free base form by following our simple straight-forward synthetic strategy.

Synthesis and Properties of Stable 20π Porphyrinoids.

The 20π porphyrinoids are immediate higher homologues of 18π porphyrins and differ from porphyrins in aromaticity which in turn affects the structure, properties and chemical reactivities. Research over the years indicated that the 20π porphyrinoids can be stabilized as non-aromatic/anti-aromatic or Mobius aromatic macrocycles using different strategies such as core-modification of porphyrins, non-metal/metal complexation of porphyrins, peripheral modification of porphyrins and expanded porphyrinoids. The structural properties such as aromaticity of the macrocycle can be controlled by choosing the right synthetic strategy.

Synthesis of -Triaryl 22-Oxanorroles.

Norroles are isomers of corroles containing a direct pyrrole N-pyrrole C link instead of a pyrrole C-pyrrole C link of corroles. 22-Oxanorroles are core-modified norroles in which one of the pyrroles is replaced with a furan ring. A straightforward route is adopted to synthesize the first examples of aromatic -triaryl-22-oxanorroles containing a pyrrole N-pyrrole α-C direct bond in 4-7% yields by condensing 16-oxatripyrrane and (1-pyrrol-3-yl)(-tolyl)methanol in CHCl under mild acid-catalyzed conditions followed by oxidation with DDQ.

Synthesis, Structure, and Properties of Helical Bis-Cu(II) Complex of Linear Hexapyrrolic Ligand.

The chemistry of metal helical complexes has attracted wide interest not only because of their resemblance with DNA structure but also due to their unique photophysical and chiroptical properties. Linear hexapyrrolic ligand has been designed and synthesized using 3-pyrrolyl BODIPY as a key precursor. The reactivity of the appended pyrrole group of 3-pyrrolyl BODIPY was taken as an advantage to synthesize bis(3-pyrrolyl BODIPY) by treating 3-pyrrolyl BODIPY with 10 equiv of acetone in CHCl under acid-catalyzed conditions and afforded bis(3-pyrrolyl BODIPY) in 20% yield.

Neo-Porphyrinoids: New Members of the Porphyrinoid Family.

The four pyrrole rings and four meso carbons of tetrapyrrolic porphyrins can be arranged in different ways and the resulting porphyrin isomers exhibit very distinct electronic properties. The extensive research carried out on the porphyrins over the years has revealed that porphyrin can have several possible isomers and some of these have been identified and synthesized. Among the porphyrin isomers synthesized so far, porphycene and N-confused porphyrins have been investigated extensively whereas the other porphyrin isomers such as hemiporphycene, corrphycene and isoporphycene remain underdeveloped because of synthetic difficulties and their inherently unstable nature.

Doubly N-Confused Calix[6]phyrin Bis-Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation.

Triplet photosensitizers that generate singlet oxygen efficiently are attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to a near-infrared (NIR) region (700 nm≈) with reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared a series of mono- and bis-palladium complexes (1-Pd-H , 2-Pd-H , 1-Pd-Pd, and 2-Pd-Pd) based on modified calix[6]phyrins as photosensitizers for singlet oxygen generation.

Singly and Doubly N-Confused Calix[4]phyrin Organoplatinum(II) Complexes as Near-IR Triplet Sensitizers.

Organoplatinum(II) complexes of calix[4]phyrin analogues, singly N-confused calix[4]phyrin (Pt-2), and doubly N-confused calix[4]phyrin (Pt-3), were synthesized and characterized. The explicit structures of these organoplatinum(II) complexes were elucidated by single-crystal X-ray diffraction and spectroscopic studies. The introduction of N-confused pyrrole rings to the parent calix[4]phyrin scaffold was found to have profound effects on the photophysical properties, such as the bathochromic shifts of both the absorption and phosphorescence maxima.

Synthesis of dimeric analogs of adenophostin A that potently evoke Ca release through IP receptors.

Inositol 1,4,5-trisphosphate receptors (IPRs) are tetrameric intracellular channels through which many extracellular stimuli initiate the Ca signals that regulate diverse cellular responses. There is considerable interest in developing novel ligands of IPR. Adenophostin A (AdA) is a potent agonist of IPR and since some dimeric analogs of IPR ligands are more potent than the corresponding monomer; we considered whether dimeric AdA analogs might provide agonists with increased potency.