Tai Peng

1,1-Hydroboration of Fused Azole–Isoindole Analogues as an Approach for Construction of B,N-Heterocycles and Azole-Fused B,N-Naphthalenes

Three isoelectronic analogues of pyrido[2,1-a]isoindole have been found to undergo a facile 1,1-hydroboration with HBMes2 borane, which provides a new and convenient method for the synthesis of B,N-heterocycles 1a-3a in high yields. Compounds 1a-3a can undergo photoelimination upon irradiation at 300 nm, generating heterocycle-fused B,N-naphthalene molecules 1b-3b, which display distinct yellow-green and blue fluorescent colors, respectively. Compound 1a undergoes thermal elimination, producing 1b at 280 °C, while compound 2a only undergoes partial elimination, forming 2b at 320 °C. Compound 3a is thermally stable up to 320 °C.

Copper(I) Complexes Bearing 1,2-Phenyl-Bridged P∧N, P∧N∧P, and N∧P∧N Chelate Ligands: Structures and Phosphorescence

With the aim to obtain new phosphorescent Cu(I) compounds, several new 1,2-phenyl-bridged P∧N, P∧N∧P, and N∧P∧N chelate ligands were designed and synthesized. These ligands were found to form complexes with Cu(I) ion readily via either solution reactions or solid-state grinding process. The new Cu(I) compounds based on this class of ligands display phosphorescence with emission color ranging from blue to red. The structure of the ligand and the nature of the N-heterocycle in the chelate ligands were found to have a significant impact on the phosphorescent properties of the Cu(I) compounds.

Bright, Multi‐responsive, Sky‐Blue Platinum(II) Phosphors Based on a Tetradentate Chelating Framework

A new class of highly efficient and stable, blue-phosphorescent PtII complexes based on a tetradentate chelating framework has been found to exhibit highly sensitive and reversible responses to multiple external stimuli including temperature, pressure, and UV irradiation with distinct phosphorescent color switching-from blue to red or white. Intermolecular excimer formation is the main origin of this intriguing multi-response phenomenon. Highly efficient singlet-oxygen sensitization by the PtII compounds yields UV-light-induced phosphorescence enhancement and color switching.

Cleavage of Unstrained C−C Bonds in Acenes by Boron and Light: Transformation of Naphthalene into Benzoborepin

Naphthalene and acenaphthene with peri 2-py and BMes2 (py=pyridyl, Mes=mesityl) substituents have been found to undergo facile phototransformation, cleavage of a C-C bond of naphthalene, and formation of 2-py-bound benzoborepins as the major products. Mechanistic pathways of this photoreaction have been established by examination of both excited and ground states by using CASSCF and CASPT2 methods in DFT and time-dependent DFT calculations. The mesityl to py-naphthyl charge-transfer transition and the mesityl migration from the boron atom to the naphthyl moiety drive this unprecedented C-C bond cleavage and boron-insertion reaction.

Triaryl-Boron Functionalized Dinuclear Platinum Complexes Linked by Photoisomerizable Bpe Ligand: Luminescence and Isomerism

We report herein a series of triarylboron-functionalized Pt(II) dinuclear complexes using a photoactive bis(4-pyridyl)ethylene (bpe) bridging unit. The new Pt(II) complexes display phosphorescence at both room temperature and 77 K. Depending on the conditions under which crystals of the complexes were grown, either the cis- or trans-isomers could be obtained. The trans and cis isomers were found to undergo light-induced isomerization in solution with the trans isomer being the dominant species.

Doping Polycyclic Arenes with Nitrogen–Boron–Nitrogen (NBN) Units

With the aid of borylation and oxidative coupling reactions, six new polycyclic aromatic hydrocarbons (PAHs) doped by nitrogen-boron-nitrogen (NBN) units were achieved. The structure-optoelectronic property relationship for this group of compounds was examined. All six compounds are fluorescent with contrasting emission colors and quantum yields.

Stimuli-Responsive B/N Lewis Pairs Based on the Modulation of B–N Bond Strength

A series of robust organoboranes with electronically tunable functionality of B/N Lewis pairs has been achieved. These compounds feature a B/N-containing core in which the interactions between the B and N atoms are modulated as a result of the structural flexibility of the nonconjugated backbone. Examination of the substituent effects of the Lewis base moiety reveals that bulky or aryl substituents favor the dynamic switching of the B-N bond in response to external stimuli, such as heat or mechanical pressure, leading to emission color modulation. This work provides a new, straightforward proof of concept toward new switchable materials design based on tunable electronic interactions.

Lanthanide Complexes with Photochromic Organoboron Ligand: Synthesis and Luminescence Study

A novel, photochromic N^C-chelate organoboron functionalized dipicolinic acid (H2L) has been designed and synthesized. Lanthanide(III) complexes based on this ligand (L) with the general formula [NBu4]3[LnL3] (Ln = Eu or Tb) were prepared. The new ligand was found to be effective in both sensitizing and photomodulating the emission of a Eu(III) ion. The photoisomerization conversion of the boryl chromophore attached to the ligand of the lanthanide complex was determined to be quantitative by NMR analysis of the La(III) analogue.