Conformationally Rigid Ethynylene-Cumulene Conjugated Aromatic [30] Heteroannulenes with NIR Absorption: Synthesis, Spectroscopic and Theoretical Characterization

NIR Absorbing Aromatic E-Ethylene Bridged Hexaphyrins (2.1.1.2.1.1): Synthesis, Characterization, and Protonation Studies

Judicious syntheses, spectroscopic analyses, and solid state structural evidence of two structural variants (with planar geometry) of strongly aromatic hybrid [30] E-ethylene bridged hexaphyrins (2.1.1.2.1.1) exhibiting strong NIR absorption are reported. The induced correspondence of fused phenanthrene on the pyrrole moieties has led to a further red-shift of up to ∼45 nm in the neutral and protonated form of the macrocycles. The electronic nature and aromaticity of both hexaphyrins are fully supported by DFT calculations.

Tailor-made aromatic porphyrinoids with NIR absorption

The highlight of this article is the recent progress in the state-of-the-art synthetic design and isolation of artificial porphyrinoids by swapping pyrrole component(s) with diverse functionalized pyrrolic(heterocyclic)/carbacycle building block(s) to compare the impact on the electronic absorption spectra and aromaticity of the incorporated isomeric/expanded porphyrinoids. Attention has been directed towards five distinct criteria of utilizing functionalized pyrrolic(heterocyclic)/aromatic hydrocarbons as synthons for NIR absorbing aromatic isomeric (N-confusion)/expanded porphyrinoids (with five/six heterocycles): (i) fused or annelated pyrrole (heterocycle), (ii) functionalized bi-pyrrole/bi-thiophene/bi-furan building blocks, (iii) azulene based carbacycle building block, (iv) vinylogous aromatic carbacycle/heterocycle(s) building block and (v) N-confused pyrrole ring(s), and N-confused fused pyrrole ring(s) leading to π-extension. These hybrid porphyrinoids are ideal candidates for basic research into macrocyclic aromaticity and for many potential applications owing to NIR absorption.

Structural isolation of NIR absorbing ferrocenyl bridged N-confused fused expanded phlorin, N-confused porphodimethene and the π-extended corrorin isomer: synthesis and characterization

Concise syntheses and spectroscopic, solid state X-ray crystal structure and theoretical studies of three electronically appealing new generation hitherto unknown ferrocenyl bridged N-confused heterocyclic macrocycles with (without) fusion are reported. Intriguingly, the expanded N-confused fused phlorin (1.1.1.1.1) with the built-in tripentacyclic [5.5.5] moiety exhibits tailing of the NIR absorption band beyond 1000 nm while the nonconjugated porphodimethene and a new generation π-extended isomeric corrorin analogue exhibit UV-vis absorption.

2,3-Diarylbenzo[b]arsole: Structural Modification and Polymerization for Tuning of Photophysical Properties

2,3-Diarylbenzo[b]arsoles were synthesized from zirconacycles and diiodophenylarsine. The structural modification to the luminophore was attained through diarylacetylene precursors, Suzuki-Miyaura coupling, and oxidation of the arsenic atom. The emission properties were controlled according to these modifications. The 2,3-diarylbenzo[b]arsoles showed aggregation-induced emission enhancement; the stronger emission was observed in the solid states than in solutions. In addition, Suzuki-Miyaura polycondensation and olefin metathesis polymerization produced main- and side-chain polymers, respectively. The resultant polymers showed different emission behaviors such as aggregation caused quenching and aggregation induced emission enhancement.

NIR absorbing aromatic (antiaromatic) vinylogous carbasapphyrins (3.3.1.0.1) with built-in fused dipolar aromatic hydrocarbon: synthesis and characterization

Variants of vinylogous core modified carbasapphyrins with a built-in fused dipolar aromatic hydrocarbon moiety paving the way to a strong diatropicity/paratropicity with vis-NIR absorption.

Tropylium cation-fused aromatic [26]dicarbaporphyrinoids with NIR absorptions: Synthesis, spectroscopic and theoretical characterization

An easy and efficient synthetic methodology for two hitherto unknown tropylium-cation-fused Hückel aromatic [26] dicarbaporphyrinoids has been developed by acid-catalyzed Lindsey type condensation of bithiophene/biselenophene diol with azulene using BF3 · Et2O followed by oxidation with chloranil and/or DDQ. Both the macrocycles have been achieved in moderately good yields. Their structures, aromaticity and optical properties have been elucidated by NMR, UV-vis-NIR spectroscopic analyses and in-depth theoretical calculations. Both the macrocycles exhibited strongly diatropic characteristics with the UV-vis spectra closely resembling the spectra for true porphyrins. Detailed structural analyses using 1H–1H COSY, ROESY and DFT level theoretical investigations indicated fully conjugated [26][Formula: see text] main conjugation pathway being benefitted by the tropylium character of the seven membered rings.