Metalated Chromene and Chromone Complexes: pH Switchable Metal–Carbon Bonding Interaction, Photo‐triggerable Chromone Delivery Application, and Antioxidative Activity

• Published in: Chemistry : a European journal Vol. 24; no. 8; pp. 1779 - 1783
• Main Authors: Ng, Sze‐Wing, Chung, Lai‐Hon, Yeung, Chi‐Fung, Lo, Hoi‐Shing, Shek, Hau‐Lam, Kang, Tian‐Shu, Leung, Chung‐Hang, Ma, Dik‐Lung, Wong, Chun‐Yuen
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 06.02.2018
• Subjects: Alkynes; Antioxidants; Antioxidants - chemistry; Carbon - chemistry; Cell Line; Cell Survival - drug effects; Chemical bonds; Chemistry; chromones; Chromones - chemistry; Coordination Complexes - chemistry; Coordination Complexes - toxicity; Coordination compounds; Drug Carriers - chemistry; Drug delivery; Drug delivery systems; Drug development; Heterocyclic compounds; Humans; Hydrogen-Ion Concentration; Irradiation; Light irradiation; Magnetic Resonance Spectroscopy; Metals; Metals - chemistry; Molecular Conformation; pH effects; Phenols; photochemistry; Radiation; ruthenium; Ruthenium - chemistry; Spectrophotometry; ruthenium; antioxidants; photochemistry; chromones; alkynes
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201705450

The two families of RuII‐chromene and ‐chromone complexes isolated in this work represent the first examples of metalated chromene and chromone complexes synthesized through transition‐metal‐mediated cyclization of phenol‐tethered ynone. These unprecedented metalated heterocyclic compounds exhibit remarkable features, such as pH‐switchable metal–carbon bonding interactions, photo‐triggerable release of organic chromone upon visible‐light irradiation, and superior antioxidative property to their organic analogue (1,4‐benzopyrone). These findings not only offer mechanistic insights into metal‐induced activation of functionalized alkynes, but also add a new dimension to rational design of antioxidants and photo‐responsive drug delivery systems. Bond maker, bond breaker: The pH‐switchable RuII‐chromene and ‐chromone complexes were successfully prepared through metal‐assisted activation of phenol‐tethered alkyne. The resulting complexes were found to exhibit low cytotoxicities in accompany with stronger antioxidative activities than their organic analogue, 1,4‐benzopyrone. Photoliberation of free chromone from the complexes was successfully demonstrated, illustrating the potential for on‐demand drug release applications.