Inverted and fused expanded heteroporphyrins.

Expanded heteroporphyrins are a class of porphyrin macrocycles containing pyrrole, thiophene, furan, selenophene and other heterocyclic rings that are connected to form an internal ring pathway containing a minimum of 17 atoms and more than 18 delocalized π electrons in their conjugated macrocyclic framework. Considering that expanded heteroporphyrins are large in size, these macrocycles are structurally flexible and prefer to adopt various conformations in which one or more pyrrole(s)/heterocycle(s) tend to be in an inverted conformation and pointed outward from the centre of the macrocyclic core. The inverted expanded heteroporphyrins are divided into two classes as follows: (1) -inverted expanded heteroporphyrins and (2) hetero-atom inverted expanded heteroporphyrins.

Investigation on heat transfer enhancement of conventional and staggered fin solar air heater coated with CNT-black paint-an experimental approach.

The present study aims at a detailed experimental study of a passive-type solar air heater (SAH) on the effect of coating the absorber plate with higher thermal conductive black paint under forced circulation method and studied under the climatic conditions of Chennai. Furthermore, to enhance the thermal performance index of conventional SAH, additional enhancement such as coating and staggered fins are fixed to the absorber plate of duct which simultaneously increases the turbulent intensity, kinetic energy to enhance the temperature of outlet air. Comparisons are made with a solar air heater without coating and staggered fin in order to assess the thermal performance.

Protonation-Triggered Hückel and Möbius Aromatic Transformations in Nonaromatic Core-Modified [30]Hexaphyrin(2.1.1.2.1.1) and Annulated [28]Hexaphyrin(2.1.1.0.1.1).

Two 1,2-diphenyl-1,2-dithienylethene-embedded hexaphyrins and containing 30π and 28π electrons, respectively, in conjugation exhibit nonaromatic characteristics. Compound shows an unusual bond length equalization in its electronic structure. However, on protonation, exhibits Hückel aromatic characteristics while shows Möbius aromatic characteristics.

Two non-identical twins in one unit cell: characterization of 34π aromatic core-modified octaphyrins, their structural isomers and anion bound complexes.

Four different core-modified planar 34π octaphyrins (, , , and ) which exhibit rotational isomerism have been synthesized and characterized both in solution and solid states. Octaphyrins , and show two inseparable isomers and which crystallize in the same unit cell. However, forms two identical isomers of .

24π Core-Modified Nonfused Pentaphyrin with Möbius Aromaticity.

Syntheses of core-modified 24π pentaphyrin 7 and 20π homoporphyrin 8 are reported. The freebase form of 7 exhibits optical and H NMR spectroscopic behavior corresponding to a 4nπ nonaromatic topology at 298 K. However, upon lowering the temperature to 188 K, 7 exhibits weak aromaticity because of a small conformational change.