An Element-Substituted Cyclobutadiene Exhibiting High-Energy Blue Phosphorescence

• 1,3,2,4-Diazadiboretidine, an isoelectronic heteroanalogue of cyclobutadiene, is an interesting chemical species in terms of comparison with the carbon system, whereas its properties have never been investigated experimentally. According to Baird's rule, Hückel antiaromatic cyclobutadiene acquires aromaticity in the lowest triplet state. Here we report experimental and theoretical studies on the ground- and excited-state antiaromaticity/aromaticity as well as the photophysical properties of an isolable 1,3,2,4-diazadiboretidine derivative. The crystal structure of the diazadiboretidine derivative revealed that the B2N2 ring adopts a planar rhombic geometry in the ground state. Yet, theoretical calculations showed that the B2N2 ring turns to a square geometry with a nonaromatic character in the lowest triplet state. Notably, the diazadiboretidine derivative has the lowest singlet and triplet states lying at close energy levels and displays blue phosphorescence.

Ämnesord

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

Nyckelord

aromaticity

DFT calculations

luminescence

main-group elements

reaction mechanisms

Butadiene

Crystal structure

Ground state

Phosphorescence

Blue phosphorescences

Chemical species

Cyclobutadienes

Photophysical properties

Rhombic geometry

Singlet and triplet state

Theoretical calculations

Theoretical study

Excited states

article

density functional theory

geometry

human experiment

practice guideline

reaction analysis

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