Mechano-Luminescent Behavior of a Pyridine-Containing Anthracene Derivative: Role of Aromatic Stacking Interactions

Abstract

Isonicotinic acid anthracen-9-ylmethylene-hydrazide (AI), prepared from anthracene-9-carboxaldehyde and isoniazid, exhibited mechano-responsive luminescent emissions; for instance, gentle pressing of the weakly emissive crystals of AI (λ em 527 nm) produced a yellow-green emissive material (λ em 540 nm). Also, the mechano-luminescent emissions of AI could be easily switched "off" upon exposure to N,N-dimethylformamide. Contrastingly, under the same conditions, benzoic acid anthracen-9-ylmethylene-hydrazide (AB) did not exhibit mechano-responsive luminescent emissions. On the basis of UV−vis, fluorescence, Fourier transform infrared spectroscopy, and powder X-ray diffraction (XRD) studies, we suggest that mechano-luminescent emissions of AI were triggered by mechanically induced deformations in the lattice, which affected the intermolecular interactions and aromatic stacking behavior. Again, the mechano-luminescent emissions of AI were switched off when mixed with oxalic acid, although accompanied by a concomitant change in color, from yellow-green to red. Single crystal XRD studies provided vital insights into the interactions of AI with oxalic acid, highlighting the role of hydrogen bonding and anion-mediated aromatic-π interactions.

The Nature and Applications of π–π Interactions: A Perspective

“…Sarma and co-workers synthesized a pyridine-containing anthracene hydrazide and studied their mechano-luminescent behavior. Deformation in the crystal lattice that leads to a change in intermolecular interactions, and π-stacking resulted in mechano-luminescent behavior of the hydrazide material . Yan et al prepared two ratiometric cocrystals (1:1 and 1:2) of 4,4′-bis­( N -carbazolyl)-1,1′-biphenyl (CBP) and 1,2,4,5-tetracyanobenzene (TCNB) that show strong π–π interactions.…”

“…Deformation in the crystal lattice that leads to a change in intermolecular interactions, and π-stacking resulted in mechano-luminescent behavior of the hydrazide material. 58 ratiometric cocrystals (1:1 and 1:2) of 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and 1,2,4,5-tetracyanobenzene (TCNB) that show strong π−π interactions. TCNB as an electron acceptor stacks with an electron donor π-conjugated CBP molecule in the 1:1 and 1:2 cocrystal.…”

Dimerization-Induced Solid-State Excimer Emission Showing Consecutive Thermochromic Luminescence Based on Acridine-Modified o-Carboranes

“…In the case of crystalline samples, the molecules are tightly packed, and there exist van der Waals interactions even in the ground state. The photoexcited “pre-associated” molecules sometimes relax to an excimeric state , which is distinguishable from ground-state aggregates. , Although there are difficulties in solid-state excimer emission due to the insufficient π overlap in the crystalline packing structure , and/or a quite low radiative rate constant originating from symmetry-forbidden transitions, several examples have been accomplished by suitable substituent group/position choice, − specific polymorphs, − and “discrete dimer” formation. − Moreover, some of them have shown stimuli responsivity based on a phase transition between “excimer on” and “excimer off” crystal-packing structures. − Another response mechanism is a gradual perturbation of excimer-state energy with a consecutive fluorescence color change, maintaining the “excimer on” state. In particular, the latter has great potential for ratiometric sensing of temperature, , pressure, and concentration .…”

Stacking among the clips of the poly-aromatic rings of phenazine with hydroxy-aromatics and photophysical properties

“…27 These interactions are common in poly-aromatic compounds to guide the mechanism of photoluminescence processes. [28][29][30] Stacked arrangements through p-interactions contribute to dimer-and excimerlike emissions [31][32][33][34] and Dexter quenching. 35 Different types of aggregates where different packings through the C-H/p interactions or p-p interactions are present show distinguishable features.…”