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Main observation and conclusion: The diastereoselective photoreactions of Ir(III)‐amine and Ir(III)‐diamine complexes are observed in the presence of O2. The Ʌ‐[Ir(pq)2(R‐mapy)](PF6) (pq is 2‐phenylquinoline and mapy is 2‐(1‐aminoethyl)pyridine) diastereomer is dehydrogenatively oxidized into imine complex Ʌ‐[Ir(pq)2(mapy‐2H)](PF6) at room temperature, while the Ʌ‐[Ir(pq)2(S‐mapy)](PF6) diastereomer occurs interligand C—N cross‐coupling reaction at 60 °C, affording a new tetradentate complex Ʌ‐[Ir(pq)(S‐pqpe)] (PF6) (pqpe is 2‐phenyl‐N‐(1‐pyridin‐2‐yl)ethyl‐quinolin‐8‐amine). The identical cases are also observed in diamine complexes Ʌ‐[Ir(pq)2(R,R‐chda)](PF6) (chda is 1,2‐diaminocyclohexane), Ʌ‐[Ir(pq)2(R,S‐chda)](PF6), and Ʌ‐[Ir(pq)2(S,S‐chda)](PF6), where the R configuration ligand is dehydrogenatively oxidized into imine, while the S configuration is retentive and the bound nitrogen atom is coupling to the C8 of pq ligand, affording Ʌ‐[Ir(pq)2(chdi)](PF6) (chdi is 1,2‐diiminocyclohexane), Ʌ‐[Ir(pq)(S‐pqchim)](PF6) (pqchim is N‐(2‐iminocyclohexyl)‐2‐phenyl‐ quinolin‐8‐amine), and Ʌ‐[Ir(S,S‐pqchda)](PF6) (pqchda is N',N"‐bis(2‐phenylquinolin‐8‐yl)cyclohexane‐1,2‐diamine), respectively. These provide a new and useful protocol for the synthesis of multidentate ligands in situ via the postcoordinated interligand‐coupling strategy under mild conditions. [ABSTRACT FROM AUTHOR]

The adhesion of silver colloids to a polyimide (PI) substrate was investigated in this study. This issue would be of concern when one tried to print electronic circuits on a flexible PI substrate. To enhance the adhesion between them, the PI surface was first roughened by using the sandblasting technique, and varying degrees of roughness were achieved using various sizes of alumina particles and various air pressures for sandblasting. The adhesion strength of silver colloids to the PI substrate after sintering was then measured according to both ASTM D4541 and ASTM 3359 standards. The results indicated that adhesion strength increased proportionally with surface roughness; however, this enhancement effect was lessened when the roughness was above 880 nm. Sintering temperature was also beneficial in increasing adhesion to the substrate; however, the electrical resistance of the silver colloids after sintering also increased with the degree of roughness. This implied that the packing of silver colloids was also affected by surface roughness. Consequently, values of surface roughness were optimal when adhesion strength and electrical resistivity were balanced. [ABSTRACT FROM PUBLISHER]

A photo-oxidation dehydrogenation reaction of enantiopure amino acid Ir(III) complexes to afford imino acid complexes was successfully developed in the presence of oxygen under mild conditions, which may involve the formation of singlet oxygen as the major reactive oxygen species and carbon-radical as an intermediate. • Enantiopure imino acid complexes were synthesized under mild conditions. • Singlet oxygen as a major reactive oxygen species was demonstrated in the photo-oxidation process. • A carbon-radical as an intermediate was demonstrated. Aerobic oxidation of amino acid complexes is an important process for the functionalization of amino acids. However, the reaction mechanism is still uncertain. Two enantiopure imino acid complexes Δ-[Ir(pq) 2 (ala-2H)] and Δ-[Ir(ppy) 2 (ala-2H)] (where pq is 2-phenylquinoline, ppy is 2-phenylpyridine and ala is alanine) have been synthesized respectively via the dehydrogenated oxidation reaction of the corresponding amino acid complexes Δ-[Ir(pq) 2 (l -ala)] and Δ-[Ir(ppy) 2 (l -ala)] in EtOH using visible light as the driving force and oxygen as an oxidant under mild conditions. The imino acid complexes have been fully characterized by NMR and MS techniques as well as X-ray single-crystal determination. The mechanism studies show singlet oxygen (1O 2) is the main reactive oxygen species (ROS) and the carbon radical intermediate may involve in the reaction process. Therefore, a reaction mechanism involving the formation of a ligand-radical intermediate rather than the higher oxidation state of the metal center was proposed. [ABSTRACT FROM AUTHOR]