Building bridges: The title compound forms an unprecedented polymeric structure with bridging B-H-B three-center two-electron bonds in the solid state. This organoborane serves as an efficient precursor for the preparation of boron-doped pi-conjugated polymers by hydroboration polymerization with a functionalized 1,4-diethynylbenzene (see picture). These polymers form thin films that show intense green luminescence.

Reduction of 2-(BMes2)pyrene (B1) and 2,7-bis(BMes2)pyrene (B2) gives rise to anions with extensive delocalization over the pyrenylene bridge and between the boron centers at the 2- and 2,7-positions, the typically unconjugated sites in the pyrene framework. One-electron reduction of B2 gives a radical anion with a centrosymmetric semiquinoidal structure, while two-electron reduction produces a quinoidal singlet dianion with biradicaloid character and a relatively large S0-T1 gap. These results have been confirmed by cyclic voltammetry, X-ray crystallography, DFT/CASSCF calculations, NMR, EPR, and UV-vis-NIR spectroscopy.

Increases in the molecular length of narrow band gap conjugated chromophores reveal potentially beneficial optical and electronic properties, thermal stabilities, and high power conversion efficiencies when integrated into optoelectronic devices, such as bulk heterojunction organic solar cells. With the objective of providing useful information for understanding the transition from small-sized molecules to polymers, as well as providing a general chemical design platform for extracting relationships between molecular structure and bulk properties, we set out to vary the electron affinity of the molecular backbone. Therefore, a series of donor (D)-acceptor (A) alternating narrow band gap conjugated chromophores were synthesized based on the general molecular frameworks: D(1)-A(1)-D(2)-A(2)-D(2)-A(1)-D(1) and D(1)-A(1)-D(2)-A(2)-D(2)-A(2)-D(2)-A(1)-D(1). When the central electron-accepting moiety (A(2)) was varied or modified, two classes of molecules could be compared. First, we showed that the alteration of one single electron-accepting group, while maintaining the shape of the molecular framework, can effectively impact the optical properties and energy levels of the molecules. DFT ground state structure optimizations show similar "U" shape conformations among these molecules. Second, we examined how the site-specific introduction of fluorine atom(s) modifies the thermal properties in the solid state, while maintaining relatively similar optical and electrochemical features of interest. Structure-property relationship of such molecular systems could be rationally evaluated in the aspects of thermal-responsive molecular organizations in the solid state and dipole moments both in the ground and excited states. The impact of molecular structure on charge carrier mobilities in field effect transistors and the performance of photovoltaic devices were also studied.

The dimethyl sulfide, pyridazine, or pyrazolide adducts of 9,10-dihydro-9,10-diboraanthracene are potent hydroboration reagents for terminal alkynes; the 1,2-diazene derivatives possess a paddle-wheel structure and are stabilised towards hydrolysis.

Boron-containing π-conjugated molecules offer a substantial application potential in the field of organic electronics. During the last decade, aryl(hydro)boranes have established themselves as versatile novel building blocks for sophisticated boron-doped materials. This perspective article comprehensively discusses key structural motifs and reactivity patterns of recently developed aryl(hydro)boranes and shows how these have been used for the synthesis of macromolecular organoboranes through hydroboration polymerisation, ring-opening polymerisation and condensation polymerisation protocols.

We report a general and selective method to synthesize 2,7-disubstituted pyrene derivatives containing two different substituents by sequential Ir-catalyzed borylation and substitution chemistry. To demonstrate the utility of our approach, we synthesized 2-cyano-7-(N,N-diethylamino)pyrene (3), a pyrene analogue of the widely studied chromophore 4-(N,N-dimethylamino)benzonitrile (DMABN). Compound 3 and the monosubstituted compounds 2-(N,N-diethylamino)pyrene (1) and 2-cyanopyrene (2) have been structurally characterized. Their electronic and optical properties have been studied by a combination of absorption and emission spectroscopies, lifetime and quantum yield measurements, and modeling by DFT and TD-DFT. The photophysical properties of 3 are compared to those of DMABN and 2-cyano-7-(N,N-dimethylamino)-4,5,9,10-tetrahydropyrene, and we show that 2,7-disubstituted pyrene is a moderately effective π-bridge for the construction of donor-acceptor compounds. It is also shown that donor or acceptor groups are only effective at the 2,7-positions of pyrene if they are suitably strong, leading to a switch in the energetic ordering of the HOMO-1 and HOMO or the LUMO and LUMO+1 of pyrene, respectively.

This case study on a series of monomeric, dimeric and polymeric Cu I chlorido NHC-picolyl complexes shows that cuprophilic interactions can ensure strong spin-orbit coupling for fast (reverse)intersystem-crossing T 1 2 S 1 and T 1 -S 0 , and therefore can serve as a design motif for the construction of highly efficient Cu I -based TADF or T 1 emitters.Luminescent molecules showing thermally activated delayed fluorescence (TADF), i.e. thermally induced reverse intersystemcrossing (RISC) T 1 -S 1 with subsequent emission from the singlet excited state S 1 -S 0 , have proven to be particularly suitable materials for OLEDs and other photonic applications, as they are able to bypass the spin-forbidden phosphorescence T 1 -S 0 . [1][2][3] In this regard, Cu I complexes with a d 10 configuration have gained a lot of attention in the last 5 years, as the absence of metal centred d-d* transitions, leading to nonradiative decay, in combination with TADF makes them competitive to Ir III -and Pt II -based emitters. [4][5][6][7][8][9][10][11][12][13][14][15][16] Although some structure-property relationships have been formulated, [17][18][19] TADF in copper complexes is still difficult to predict a priori, let alone to design TADF materials, as it is an excited state property. In contrast, cuprophilic interactions can be prearranged in the ground state by careful choice of the ligand environment, and they have been shown to allow, albeit inefficiently, phosphorescence in simple dinuclear Cu I complexes with bridging diphosphines and other systems, 20-23 and also in clusters. [24][25][26] A few dicopper(I) complexes with short Cu-Cu contacts (o2.8 Å) have been reported to emit efficiently via TADF, but the influence of cuprophilic interactions in those has yet not been addressed. 4,8,19,[27][28][29] In this case study on a family of new bidentate copper(I) NHC-picolyl complexes we show that cuprophilic interactions can greatly enhance the radiative rate constants of the T 1 state by increasing spin-orbit coupling (SOC), giving emission lifetimes comparable to TADF, and can even be involved in the luminescence mechanisms when TADF is present. Thus, cuprophilic interactions provide a design methodology for highly efficient Cu I emitters.For this study, we have prepared a series of Cu I NHC-picolyl complexes (1-7, Fig. 1) by a facile one-step silver-free procedure from azolium chlorides in aqueous ammonia as basic and copper complexing medium (see ESI †). 30 The azolium salts include new picolyl linkers, functionalized in the para position Fig. 1 Chemical structures of complexes 1-7, for dimers representative molecular structure of 1 obtained from X-ray diffraction and intermolecular Cu-Cu distances of 1-4.

n ) and its SMe 2 adduct 1(SMe 2 ) 2 are readily reduced with lithium in THF to the dianionic 9,10-diborataanthracene Li 2 [1]. An X-ray crystal structure analysis of (Li(thf ) 2 ) 2 [1] revealed monomeric inverse sandwich complexes, each of them containing two Li(thf ) 2 moieties coordinated to both sides of the central B 2 C 4 ring. Compared to 9,10-dimethyl-9,10-dihydro-9,10-diboraanthracene, the four B-C Ar bonds of (Li(thf ) 2 ) 2 [1] are shorter by 0.046(4) A ˚, thereby indicating an increased degree of BdC Ar double-bond character. Consequently, (Li(thf ) 2 ) 2 [1] reacts with 4,4 0 -dimethylbenzophenone as a BdC Ar -C Ar dB diene and undergoes a [4þ2] cycloaddition reaction with formation of a bicyclic product. In contrast, tert-butylacetylene reacts with (Li(thf ) 2 ) 2 [1] under formal 1,4-addition of its methinic C-H group instead of its CtC triple bond to the two boron atoms.