Mechanochromic luminescence based on a phthalonitrile-bridging salophen zinc() complex

• Published in: New journal of chemistry 2019-10, Vol.43 (4), p.15886-15891
• Main Authors: Yan, Xianju, Song, Xiaoxian, Mu, Xiaoyue, Wang, Yue
• Format: Article
• Language: English
• Subjects: Emission analysis; External pressure; Luminescence; Mechanoluminescence; Morphology; Properties (attributes); Stimuli; X ray powder diffraction; Zinc compounds
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c9nj03704g

A 4,5-diaminophthalonitrile based zinc( ii )-salophen complex CN-Zn was designed and synthesized with obvious mechanochromic properties to meet application demands for stimuli-responsive luminescent materials composed of cost-efficient organometallic molecules. CN-Zn solid exhibits reversible luminescence color alteration between vibrant yellow and orange (emission maximum from λ max = 560 nm to λ max = 591 nm) after first being mechanically ground and then treated by organic vapor fuming. The process is repeatable and highly sensitive, which makes CN-Zn a potential sensor of both external pressure and organic volatile gases. Thermal annealing of the ground CN-Zn powder at 150 °C and 230 °C resulted in red emission ( λ max = 611 nm) and orange emission ( λ max = 599 nm), respectively. Investigations were conducted using photophysical analyses, powder X-ray diffraction (XRD), and thermal testing (DSC and TGA) to apprehend the mechanism behind the stimuli-responsive properties. The results demonstrate that external treatment can lead to a packing mode transformation between the crystalline and amorphous phase in CN-Zn , thus creating morphology dependent emission features. In view of all properties, CN-Zn is a promising option for cost-efficient stimuli-responsive materials. Here, we showcase the impressive stimuli-responsive properties of a luminescent zinc( ii )-salophen complex CN-Zn , highlighting a reversible mechanochromic property.