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N-heterocyclic carbene (NHC)–gold and –silver complexes have attracted the interest of the scientific community because of their multiple applications and their versatility in being chemically modified in order to improve their biological properties. However, most of these complexes contain one or more chiral centers, and have been obtained and studied as racemic mixture. In particular, concerning the interesting biological and medicinal properties, many questions about how the chirality may influence these properties still remain unanswered. Aiming at a better understanding, herein a series of enantiopure NHC–gold and –silver complexes was synthesized, characterized and biologically evaluated in different in vitro systems. The individuated complexes exerted different properties based on the complexed metal and the specific configuration, with the (R)-gold–NHC complexes being the most active, particularly as anti-inflammatory molecules. Docking simulations indicated a different binding mode for each enantiomer. Moreover, anticancer and antibacterial activities were also evaluated for the considered enantiomers. Overall, the reported data may contribute to a better understanding of the different biological properties exerted by the enantiopure gold and silver complexes. [ABSTRACT FROM AUTHOR]

The reaction of CuX (X = I, Br, Cl) with ( S , S )- i Pr-pheboxH = 1,3-bis[4′-( S )-isopropyloxazolin-2′-yl]benzene in 2:1 molar ratio allows us to synthesize tetranuclear complexes [Cu 4 X 4 (к 2 - N , N - i Pr-pheboxH) 2 ] (X = Cl ( 1 ), Br ( 2 ), I ( 3 )). The polymeric species [Cu 4 I 4 (κ 2 - N , N - i Pr-pheboxH) 2 ] n ( 4 ) has been prepared by reaction of CuI with ( S , S )- i Pr-pheboxH in 1.5:1 molar ratio. Also, polymeric silver species {[Ag(κ 2 - N , N - i Pr-pheboxH)][X]} n (X = CF 3 SO 3 ( 7a ), SbF 6 ( 7b ), PF 6 ( 7c )) have been synthesized by reaction of the corresponding silver salt and ( S , S )- i Pr-pheboxH in 1:1 molar ratio. The structures of the tetranuclear complexes 1 – 3 as well as of the polymeric species [Cu 4 I 4 (κ 2 - N , N - i Pr-pheboxH) 2 ] n ( 4 ) and {[Ag(κ 2 - N , N - i Pr-pheboxH)][PF 6 ]} n ( 7c ) have been determined by single crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of the racemic chiral methyl complex (η5-C5H5)Re(NO)(PPh3)(CH3) (1) with CF3SO3H and then NH2CH2C6H5 gives [(η5-C5H5)Re(NO)(PPh3)(NH2CH2C6H5)]+ ([4a-H]+ ; 73%), and deprotonation with t-BuOK affords the amido complex (η5-C5H5)Re(NO)(PPh3)(NHCH2C6H5) (76%). Reactions of 1 with Ph3C+ X− and then primary or secondary amines give [(η5-C5H5)Re(NO)(PPh3)(CH2NHRR′)]+ X− ([6-H]+ X−; R/R′/X= a, H/NH2CH2C6H5/BF4; a′, H/NH2CH2C6H5/PF6; b, H/NH2CH2(CH2)2CH3/PF6; c, H/(S)-NH2CH(CH3)C6H5/BF4); d, CH2CH3/CH2CH3/PF6; e, CH2(CH2)2CH3/CH2(CH2)2CH3/PF6; f, CH2C6H5/CH2C6H5/PF6; g, -CH2(CH2)2CH2-/PF6; h, –CH2(CH2)3CH2–/PF6; i, CH3/CH2CH2OH/PF6 (62–99%). Deprotonations with t-BuOK afford the amines (η5-C5H5)Re(NO)(PPh3)(CH2NRR′) (6a–i; 99–40%), which are more stable and isolated in analytically pure form when R≠H. Enantiopure 1 is used to prepare (R Re S C)-[6c-H]+ , (R Re S C)-6c, (S)-[6g-H]+ , and (S)-6g. The crystal structures of [4a-H]+ , a previously prepared NH2CH2Si(CH3)3 analog, [6a′,d,f,h-H]+ , (R Re S C)-6c, and 6f are determined and analyzed in detail, particularly with respect to cation/anion hydrogen bonding and conformation. In contrast to analogous rhenium containing phosphines, 6a–i show poor activities in reactions that are catalyzed by organic amines. [Copyright &y& Elsevier]

Despite hundreds of cationic bis-cyclometalated iridium(III) complexes having been explored as emitters for light-emitting electrochemical cells (LEECs), uniformly their composition has been in the form of a racemic mixture of Λ and Δ enantiomers. The investigation of LEECs using enantiopure iridium(III) emitters, however, remains unprecedented. Herein, we report the preparation, the crystal structures, and the optoelectronic properties of two families of cyclometalated iridium(III) complexes of the form of [(C^N) 2 Ir(dtBubpy)]PF 6 (where dtBubpy is 4,4'-di-tert-butyl-2,2'-bipyridine) in both their racemic and enantiopure configurations. LEEC devices using Λ and Δ enantiomers as well as the racemic mixture of both families have been prepared, and the device performances were tested. Importantly, different solid-state photophysical properties exist between enantiopure and racemic emitters, which are also reflected in the device performances.