Discovered by Stock and Pohland in 1926, borazine is the isoelectronic and isostructural inorganic analogue of benzene, where the C[double bond, length as m-dash]C bonds are substituted by B-N bonds. The strong polarity of such heteroatomic bonds widens the HOMO-LUMO gap of the molecule, imparting strong UV-emitting/absorption and electrical insulating properties. These properties make borazine and its derivatives valuable molecular scaffolds to be inserted as doping units in graphitic-based carbon materials to tailor their optoelectronic characteristics, and specifically their semiconducting properties. By guiding the reader through the most significant examples in the field, in this feature paper we describe the past and recent developments in the organic synthesis and functionalisation of borazine and its derivatives. These boosted the production of a large variety of tailored derivatives, broadening their use in optoelectronics, H2 storage and supramolecular functional architectures, to name a few.

The first rational synthesis of a BN-doped coronene derivative in which the central benzene ring has been replaced by a borazine core is described. This includes six C-C ring-closure steps that, through intramolecular Friedel-Crafts-type reactions, allow the stepwise planarization of the hexaarylborazine precursor. UV/Vis absorption, emission, and electrochemical investigations show that the introduction of the central BN core induces a dramatic widening of the HOMO-LUMO gap and an enhancement of the blue-shifted emissive properties with respect to its all-carbon congener.

ABSTRACT:The divergent synthesis of two series of borazino--doped polyphenylenes, in which one or more aryl units are replaced by borazine rings, is reported for the first time taking advantage of the decarbonylative [4+2] Diels--Alder cy--cloaddition reaction between ethynyl and tetraphenylcyclopentadienone derivatives. Owing to the possibility of function--alizing the borazine core with different groups on the aryl substituents at the N and B atoms of the borazino core, we have prepared borazino--doped polyphenylenes featuring different doping dosages and orientations. To achieve it, two molecu--lar modules were prepared: a core and a branching unit. Depending on the chemical nature of the central aromatic mod--ule and of the reactive group, each covalent combination of the modules yields one exclusive doping pattern. Indulging this approach, three-- and hexa--branched hybrid polyphenylenes featuring controlled orientation and dosages of the dop--ing B 3 N 3 --rings have been prepared. Detailed photophysical investigations showed that upon increasing the doping dosage, the strong luminescent signal is progressively reduced. This suggests that the presence of the B 3 N 3 --rings engages addi--tional deactivation pathways possibly involving excited states with an increasing charge separate character that are re--stricted in the full--carbon analogues. Notably, a strong effect of the orientational doping on the fluorescence quantum yields was observed for those hybrid polyphenylene structures featuring low doping dosages. At last, we showed that Cu--catalyzed 1,3--dipolar cycloaddition is also chemically compatible with the BN core, further endorsing the inorganic ben--zene as a versatile aromatic scaffold to engineering molecular materials with tailored and exploitable optoelectronic properties.

The first rational synthesis of a BN-doped coronene derivative in which the central benzene ring has been replaced by a borazine core is described. This includes six CÀC ringclosure steps that, through intramolecular Friedel-Crafts-type reactions, allow the stepwise planarization of the hexaarylborazine precursor. UV/Vis absorption, emission, and electrochemical investigations show that the introduction of the central BN core induces a dramatic widening of the HOMO-LUMO gap and an enhancement of the blue-shifted emissive properties with respect to its all-carbon congener. Figure 1. HBC and its borazino-doped analogue HBBNC. Rue de Bruxelles 61, Namur 5000 (Belgium) Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.doi.org/10.1002/anie.201700907. Scheme 1. Retrosynthetic strategies toward HBBNC.

The hydroformylation remains the most applied industrial process to produce aldehydes. Much research has been devoted to developing new catalyst systems since aldehydes are highly desired. Supported metal catalyst complexes have drawn renewed attention due to an increased interest in benign and environmental processes. In this paper, NiXantphos has been immobilized on hyperbranched poly(aryleneoxindole) supports, different in linker, via a one-step post-functionalization. Two heterogeneous hyperbranched poly(aryleneoxindole) supported NiXantphos ligands were evaluated in the microwave assisted rhodium catalyzed hydroformylation of olefins. After selecting the best reaction conditions, a variety of functionalized olefins was successfully converted into the desired linear aldehydes working under milder conditions compared to known processes, in terms of syngas pressure (4.8 bar), temperature (75 °C) and reaction times (20 min). The increased activity might emanate from a positive dendritic effect unique to the dendritic nature of the support. Furthermore, the catalyst system was successfully