Synthesis, functionalization and coordination chemistry of dibenzotetraaza[14]annulenes

This comprehensive review summarizes recent advances in the synthesis and coordination chemistry of dibenzotetraaza[14]annulenes (DBTAAs) reported between 2010 and 2021. Owing to the smaller N4 donor cavity compared to that of the porphyrin core, it is not surprising that DBTAA offers versatile and unique coordination modes towards metal ions. The structural modification of the DBTAA core allows for the fine-tuning of their spectroscopic properties. DBTAA and derivatives have been utilized across a wide range of research disciplines such as in electronic devices and biological assays. The feasible preparation of ligands and their metal complexes suggests DBTAAs as potential alternatives to porphyrins

Synthesis and crystallographic characterisation of pyridyl- and indoleninyl-substituted pyrimido[1,2-b]indazoles

Pyridyl- and indoleninyl-substituted pyrimido[1,2-b]indazole were synthesised in good to high yields from the condensation reaction of 1,3-dialdehydes with 3-aminoindazoles. The structural features of the compounds were determined by NMR (1H, 13C and 19F), FT-IR and HR-MS. The spectroscopic assignments were confirmed by X-ray crystallography for two derivatives, i.e., 9-Bromo-3-(pyridin-4-yl)pyrimido[1,2-b]indazole (1b) and 10-Methoxy-3-(pyridin-4-yl)pyrimido[1,2-b]indazole (1c), which further provides support for significant delocalisation of π-electron density over the entire fused ring system. The molecular packing was assessed by conventional methods together with Hirshfeld surface analyses. In 1b, the molecular packing features pyrimidyl-N–H···N(pyrimidyl), π(pyrazolyl)···π(pyrimidyl) and Br···N interactions within a two-dimensional array. In 1c, pyrimidyl-C–H···N(pyrazolyl) and pyridyl-C–H···O(methoxy) interactions feature within a three-dimensional architecture

Indoleninyl-substituted pyrimido[1,2-b]indazoles via a facile condensation reaction

A new series of pyrimido[1,2-b]indazoles bearing indolenine moieties was synthesized through a simple condensation reaction with up to 94% yield. The present method features the versatile formation of a pyrimidine ring with a broad range of substrates, great functional group compatibility and facile synthetic operation. The work offers opportunities in drug development as well as in materials scienc

Supramolecular assembly and spectroscopic characterization of indolenine–barbituric acid zwitterions

A series of indolenine and barbituric acid zwitterion scaffolds were synthesized with a maximum yield of 98% via the formation of C–C single bond. The structures were unambiguously elucidated by various spectroscopic techniques such as 1H, 13C NMR (1D, 2D), FT-IR and high-resolution mass spectrometry (HRMS). Single crystal X-ray crystallography analysis on 22, as the 22.DMF 1:1 solvate, confirms the presence of wellseparated iminium and enolate centres, and also confirms that the BA ring is highly twisted with respect to the indolenine ring due to steric hindrance. The presence of N–H∙∙∙O and N–H∙∙∙O- groups favour a 1D-supramolecular assembly in the solid-state. The orange or yellow solutions of the zwitterion exhibit an intense molar absorption coefficient, ε ranging between 0.21 × 104 and 2.93 × 104 M-1 cm-1 in the UV-vis region. Furthermore, the Intramolecular Charge Transfer (ICT) peak of zwitterion displays a hypsochromic shift in absorption behavior when the polarity of the solvent increases. Moreover, treatment of small amount of trifluoroacetic acid (TFA) to the DMF solution of 19 resulted in the protonation of an enolate of BA ring. This fundamental work provides valuable structural design and information for the construction of supramolecular chemistry and synthetic dyes based on indolenine substituted BA derivatives

Indolenine – dibenzotetraaza[14]annulene nickel complexes as sensitizers for DYE – sensitized solar cells / Abdul Qaiyum Ramle

A new series of macrocyclic nickel complexes having indolenine and dibenzotetraaza[14]annulene (DBTAA) moieties were synthesized and tested for their application as sensitizers in dye-sensitized solar cells (DSSCs). The structures are furnished with anchoring groups of ethyl ester (8a, 8b, and 8c) or carboxylic acid (9c) on the indolenine moiety and hexyloxy (8b) or neopentyloxy (8c, 9c) groups on the DBTAA moiety. The best performance was exhibited by dye 9c, which under constant AM 1.5G solar simulation (100 mW cm-2) using I-/I3- electrolyte gave a short-circuit current Jsc = 0.43 mA cm-2, an open-circuit voltage Voc = 0.41 V and a fill factor FF = 0.528, corresponding to an overall conversion efficiency of η = 0.093%. The dyes 8c and 9c were studied by electrochemical impedance spectroscopy (EIS) and incident-photon-to-current-conversion efficiency (IPCE). This is the first investigation of anti-aromatic (4n π-electrons) macrocyclic DBTAA derivatives as sensitizers for DSSCs applications

Synthetic strategies and diversification of dibenzo[1,5]diazocines

Dibenzo[1,5]diazocine scaffolds are present in a wide range of organic building blocks, for example in pharmaceuticals, materials and structural chemistry. However, the development of these structural frameworks has not received significant attention owing to limited synthetic protocols and strategies. Herein, a summary of the attractive synthetic approaches for the construction of dibenzo[1,5]diazocines, epiminodibenzo[1,5]diazocines and epoxydibenzo[1,5]diazocines developed over the past two decades is presented. The spectroscopic, synthetic mechanisms for the formation of the heterocyclic rings and remarkable structural features, including in the solid-state, are discussed

Indolenine – dibenzotetraaza [14] annulene Ni (II) complexes as sensitizers for dye - sensitized solar cells

A new series of macrocyclic Ni (II) complexes having indolenine and dibenzotetraaza [14] annulene (DBTAA) moieties were synthesized and tested for their application as sensitizers in dye - sensitized solar cells (DSSCs). The structures are furnished with anchoring groups of ethyl ester (8a, 8b, and 8c) or carboxylic acid (9c) on the indolenine moiety and hexyloxy (8b) or neopentyloxy (8c, 9c) groups on the DBTAA moiety. The best performance was exhibited by dye 9c, which under constant AM 1.5G solar simulation (100 mW cm −2 ) using I − /I 3 − electrolyte gave a short-circuit current J sc = 0.43 mA cm −2 , an open-circuit voltage V oc = 0.41 V and a fill factor FF = 0.528, corresponding to an overall conversion efficiency of η = 0.093%. This is the first investigation of macrocyclic DBTAA derivatives as sensitizers for DSSCs applications. © 2019 Elsevier Lt