Organometallic copper(II) complex of meso-meso N-methyl N-confused pyrrole-bridged doubly N-methyl N-confused hexaphyrin.

Synthesis, spectroscopic and theoretical characterization of a hitherto unknown meso-meso N-confused N-methylpyrrole-bridged doubly N-confused hexaphyrin (molecule 5) and its organometallic copper(II) complex (molecule 6) are reported herein. The absence of Q-type bands in the UV-Vis spectrum and the high chemical shifts of the inner proton signals of 5 suggest its globally non-aromaticity. The spectroscopic evidence of non-aromaticity for 5 and the paramagnetic nature of 6, are fully supported by density functional theory (DFT) calculations of the UV-Vis spectra, electron paramagnetic resonance (EPR) g-tensor parameters, and the magnetically induced current density strengths obtained with the gauge-including magnetically induced currents (GIMIC) method.

Rational and controllable syntheses of variants of modified N-confused N-fused porphodimethenes and a porphotrimethene with adaptive properties.

Retrosynthetic design and synthesis with structural isolation of two unprecedented core modified N-confused N-fused porphodimethene-like porphyrinoids possessing a [5.5.5.5] tetracyclic ring with tunable photophysical properties is reported. The solid-state X-ray crystal structure reveals the expected cis geometry for the meso-sp3 carbons. Controlled chemical oxidation of the porphodimethene analogue 11 bearing the N-confused pyrrole moiety to the corresponding porphotrimethene 12 has been achieved in quantitative yield, while 10 bearing the N-methyl N-confused pyrrole moiety remained unsusceptible to chemical oxidation. All three S2N3 hybrid N-confused N-fused porphodi(tri)methene-like porphyrinoids 10-12 could recognize the fluoride anion with high selectivity; however, porphodimethene 10 and porphotrimethene 12 do so via deprotonation rather than an anion recognition based mechanism as has been anticipated in the case of porphodimethene 11.

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.

Fluoride ion coordination-induced turn-on fluorescence of tailored N-methyl N-confused tripyrromonomethene analogues.

Structural isolation of two unprecedented AIEE/ACQ type fluorophores based on N-methyl N-confused tripyrromonomethene analogues exhibiting selective F- anion-coordination-induced-enhanced emission (ACIEE) with a detection limit of 10-7 M is reported. The intrinsic relation between molecular structures/molecular arrangements with (without) anion binding have been revealed at a deeper level via spectroscopic measurements and DFT level theoretical studies.

Metalloceneincorporated Hybrid Singly N-Methyl N-Confused Calixphyrins: Synthesis, Characterization, Protonation and Deprotonation Studies.

Rational design and isolation of two hitherto unknown highly stable single conformer of ferrocene incorporated meso-aryl substituted singly N-methyl N-confused-calixphyrins have been achieved in quantitative yields. The solid-state crystal structure reveals the obvious trans-geometry for the meso-protons with the possibility for both the macrocycles to exist either racemic or enantiomer forms. However, thorough solution-state spectroscopic characterization strongly concludes the experimental isolation of a single isomer for both the macrocycles. The drastic modification of UV-vis spectral patterns upon imine pyrrole N protonation and amine pyrrole NH deprotonation of both the calixphyrins could pave way for these macrocycles to act as opto-electronic materials. The conformational preorganization and protonation and deprotonation induced conformational reorganization have been extensively studied by solution state spectroscopic techniques, solid state X-ray crystal structure and in depth DFT level theoretical 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.

Perimeter Coordinated Diastereomeric Rh(I) Complex of Helically Twisted Weakly Aromatic Hybrid Singly N-Confused ß-ß Fused Ferrocenoporphyrinoids.

Expedient synthesis, spectroscopic, solid state structural proof, and theoretical study of helically twisted weakly aromatic hybrid singly N-confused ferrocenoporphyrinoids and the peripheral coordinated Rh(I) complex are reported. The X-ray crystal structure of the macrocycles reveals an ambiguously inverted pyrrole ring reinforcing regioselective ß,ß-linkage with the spatially adjacent N-confused N-methyl pyrrole ring leading to endocyclic extension of macrocyclic π-conjugation via tricyclic [5.5.5] moiety. The three-dimensional structure with built-in fused tricyclic [5.5.5] moiety has paved way to three-dimensional weak diatropicity with vis-NIR absorptions. The peripheral coordinated Rh(I) complex owing to helical chirality about the macrocyclic ring and planar chirality about the square planar Rh coordination site exists as a mixture of diastereomers (5:3) with well resolved 1H NMR spectra anticipating weak aromaticity. The experimental spectroscopic measurements are in agreement with theoretically determined electronic structure and properties strongly elucidating sustained weak diatropic ring currents in twisted macrocycles both in neutral form and in the metalated complex. Further fragment molecular orbital approach and molecular orbital theory gave insights on the stability of N-confused ß-ß fused oxo-ferrocenoporphyrinoids and formation of the selective peripheral coordinated Rh(I) complex.

Targeted synthesis of meso-aryl substituted aromatic trans-doubly N-confused dithia/diselena [18] porphyrins (1.1.1.1) with NIR absorption: spectroscopic and theoretical characterization.

High yield synthesis and spectroscopic isolation of two hitherto unknown highly stable single conformers of meso-aryl substituted dithia/diselena trans-doubly N-confused porphyrins with fully π-conjugated [18] annulene structures are reported. In-depth solution state spectroscopic measurements and DFT level theoretical calculations strongly show the distinct aromaticity with strong NIR absorption of these new macrocycles.

Comparative in†vitro Studies of the Topoisomerase I Inhibition and Anticancer Activities of Metallated N-Confused Porphyrins and Metallated Porphyrins.

Using the original approach, a series of metallated N-confused porphyrins and metallated porphyrins have been synthesized and characterized. For all the synthesized porphyrins, in vitro studies of cytotoxic activity against K562, U937, HL-60, Jurkat, A549 and HeLa cancer cell lines, the ability to induce apoptosis and effects on the cell cycle as well as the kinetics of proliferative activity of porphyrins and their respective metallated complexes in real time have been developed. The inhibitory activity of metallated porphyrins against human topoisomerase I and the possible mechanism of inhibition have been carried out by modelling using molecular docking.

Redox-Associated Variation of Hückel Aromaticity from Lactam-Embedded Smallest Antiaromatic trans-Doubly N-Confused Porphyrins: Synthesis and Characterization.

High-yield synthesis, spectroscopic and solid-state structural proof of the lactam-embedded smallest ever metal-free stable Hückel antiaromatic trans-doubly N-confused [16] porphyrins are reported. These new facets of trans-doubly N-confused porphyrins have been anticipated to exhibit the redox-associated variation of Hückel aromaticity as a mere consequence of the amido-like structures of the N-confused N-methyl pyrrole rings of the macrocycles. Strong aromaticity upon NaBH4 reduction leading to a resonance dipolar structure of the [18]π-conjugated system as the reduced congener with concomitant Hückel topology are the important highlights. Excellent agreement between experimental spectroscopic measurements and the theoretically determined properties elucidate aromaticity switching upon chemical reduction. Recent years have witnessed an upsurge of demand for the experimental realization of stable antiaromatic systems because of their versatile applications in material science. The conformational rigidity and the enriched stability of these novel 16π antiaromatic doubly N-confused porphyrins might entitle these macrocycles toward such applications.

meso-Aryl substituted stable unorthodox 5,10-porphodimethenes with α,ß and ß,ß-N-methyl pyrrole connectivities: synthesis and spectroscopic, solid state and theoretical characterization.

A concise and convenient synthetic methodology leading to an unambiguous isolation of two hitherto unknown highly stable single conformers of meso-aryl substituted unorthodox 5,10-porphodimethenes has been developed by the inclusion of N-methyl pyrrole units with α,ß and ß,ß-linkages into the core of heterocyclic macrocycles.

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

Two hitherto unknown conformationally rigid Hückel aromatic ethynylene-cumulene conjugated [30] heteroannulenes have been synthesized and characterized. A thorough solution-state spectroscopic characterization, combined with in-depth theoretical calculations, has been performed to arrive at the proposed geometry of the macrocycles. The most stable optimized structures for the free base form of both the macrocycles showed absolute planar geometries without any ring inversion with mean plane deviation (MPD) values of 0.00 and 0.00 Å, respectively, in accordance with the NMR spectroscopic observations. The induced correspondence of rigid ethynylene-cumulene moieties leading to near-infrared (NIR) absorption in neutral and protonated forms of macrocycles is the important highlight of this article. This noteworthy finding has been supported by DFT-level theoretical calculations. There is an increasing pursuit in designing such NIR-absorbing/-emitting systems due to their immense applications in medicine and biology for recognizing and transportation of various substrates. The geometry of the novel 30π aromatic heteroannulenes shows promise for evolution of such novel systems in near future.

Conformational-Switch Based Strategy Triggered by [18] π Heteroannulenes toward Reduction of Alpha Synuclein Oligomer Toxicity.

A water-soluble meso-carboxy aryl substituted [18] heteroannulene (porphyrin) and its Zn-complex have been found to be viable in targeting α-Syn aggregation at all its key microevents, namely, primary nucleation, fibril elongation, and secondary nucleation, by converting the highly heterogeneous and cytotoxic aggresome into a homogeneous population of minimally toxic off-pathway oligomers, that remained unexplored until recently. With the EC50 and dissociation constants in the low micromolar range, these heteroannulenes induce a switch in the secondary structure of toxic prefibrillar on-pathway oligomers of α-Syn, converting them into minimally toxic nonseeding off-pathway oligomers. The inhibition of the aggregation and the reduction of toxicity have been studied in vitro as well as inside neuroblastoma cells.

Neutral Porphyrin Derivative Exerts Anticancer Activity by Targeting Cellular Topoisomerase I (Top1) and Promotes Apoptotic Cell Death without Stabilizing Top1-DNA Cleavage Complexes.

Camptothecin (CPT) selectively traps topoisomerase 1-DNA cleavable complexes (Top1cc) to promote anticancer activity. Here, we report the design and synthesis of a new class of neutral porphyrin derivative 5,10-bis(4-carboxyphenyl)-15, 20-bis(4-dimethylaminophenyl)porphyrin (compound 8) as a potent catalytic inhibitor of human Top1. In contrast to CPT, compound 8 reversibly binds with the free enzyme and inhibits the formation of Top1cc and promotes reversal of the preformed Top1cc with CPT. Compound 8 induced inhibition of Top1cc formation in live cells was substantiated by fluorescence recovery after photobleaching (FRAP) assays. We established that MCF7 cells treated with compound 8 trigger proteasome-mediated Top1 degradation, accumulate higher levels of reactive oxygen species (ROS), PARP1 cleavage, oxidative DNA fragmentation, and stimulate apoptotic cell death without stabilizing apoptotic Top1-DNA cleavage complexes. Finally, compound 8 shows anticancer activity by targeting cellular Top1 and preventing the enzyme from directly participating in the apoptotic process.

Ethynylene-linked Figure-Eight Octaphyrin(1.2.1.1.1.2.1.1): Synthesis and Characterization of Its Two Oxidation States.

An octaphyrin(1.2.1.1.1.2.1.1) containing two conjugated ethynylene bridges has been synthesized and characterized. The macrocycle reveals complex conformational dynamics dependent on its protonation and oxidation state. The [40]annulenoid macrocycle and its [38]annulenoid oxidized form display residual macrocyclic ring currents. In spite of its low apparent aromaticity the new octaphyrin is a potent chromophore with a vis-NIR absorption profile strongly influenced by the redox and acid-base chemistry.

Protonation Dependent Topological Dichotomy of Core Modified Hexaphyrins: Synthesis, Characterization, and Excited State Dynamics.

Two hitherto unknown core modified hexaphyrin analogues have been synthesized and characterized where the conformational dynamics of these macrocycles in the free base form is achieved by the rotation of thienothiophene units. Further unique property of these macrocycles is the Hückel-Möbius topological switching. The thermodynamic equilibrium and kinetics of the interconversion leading to Hückel-Möbius switches have been triggered by external stimuli, such as protonation and/or temperature. We have provided a thorough solution-state spectroscopic characterization, solid-state structural evidence combined with in-depth theoretical calculations to investigate the crucial factors involved in such interconversion between Hückel and Möbius topologies for these hexaphyrins which will be useful in designing future new members to expanded porphyrin chemistry.

Aromatic Fused [30] Heteroannulenes with NIR Absorption and NIR Emission: Synthesis, Characterization, and Excited-State Dynamics.

Two hitherto unknown planar aromatic [30] fused heterocyclic macrocycles (1.1.0.1.1.0), with NIR absorption in free-base form and protonation-induced enhanced NIR emission, have been synthesized from easy to make precursors. The induced correspondence of fusion on the macrocyclic structure, electronic absorption, and emission spectra have been highlighted.

Induced Correspondence of a Local π-Aromatic Sextet in Heteroannulenes: Synthesis and Characterization.

Acid-catalyzed [3+3] condensation reactions of two hitherto unknown tripyrrane moieties with pentafluorobenzaldehyde has led to the formation of new generation heteroannulene (4.1.4.1) and mutant heteroannulene (1.1.1.1.1.1). Inclusion of local π-aromatic sextets, namely the N-methyl pyrrole rings through ß,ß-linkages and α,ß-linkages, has led to the isolation of first ever heteroannulenes cross-conjugated at four points and two points respectively within the macrocycles.

Möbius Aromatic Core-Modified Heterocyclic [20]†Macrocycles (4.1.1) with a Protruding N-Methyl Pyrrole Ring.

Herein, we report the first synthesis of an unorthodox tripyrrane moiety from the regioselective ß-benzoylation of pyrrole and the acid-catalyzed condensation of the desired precursors. A [3+1] Mac Donald type condensation strategy for this tripyrrane has led to the exclusive isolation of two hitherto-unknown aromatic [20] heterocyclic macrocycles (4.1.1).