화학공학소재연구정보센터
Inorganic Chemistry, Vol.57, No.4, 2249-2259, 2018
Synthesis and Characterizations of Macrocyclic Cr(III) and Co(III) 1-Ethynyl Naphthalene and 9-Ethynyl Anthracene Complexes: An Investigation of Structural and Spectroscopic Properties
Reported herein are the syntheses and structural and emission spectroscopic characterizations of new Cr-III(HMC) and Co-III(cyclam) complexes bearing fluorophore alkynyl ligands, where HMC and cyclam are 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane and 1,4,8,11-tetraazacyclotetradecane, respectively. Two Cr(III) bis-1-ethynylnaphthalene (C2Np) complexes, trans-[Cr(HMC)(C2Np)(2)]Cl ([1]Cl) and cis-[Cr(HMC)(C2Np)(2)]Cl ([2]Cl), were prepared from the reactions between trans/cis-[Cr(HMC)Cl2]Cl and lithium 1-ethynylnaphthalene (LiC2Np) in yields of 73 and 66%, respectively. Also investigated are Co-III(cyclam) complexes bearing both C2Np and C(2)ANT (ANT = 9-anthryl), namely [Co(cyclam)(C2Ar)Cl]Cl (Ar = ANT ([3]Cl), Np ([4]Cl)), [Co(cyclam)(C2Np)(NCCH3)](OTf)(2) ([5](OTf)(2)), and [Co(cyclam)(C2Np)(2)]OTf ([6]OTf). Complexes [3]Cl (72%) and [4]Cl (67%) were prepared from the reaction between [Co(cyclam)Cl-2]Cl and Me(3)SiC(2)ANT or Me3SiC2Np, respectively, in the presence of triethylamine. The reaction of [4]Cl with excess silver triflate in CH3CN yielded complex [5](OTf)(2) (78%), which was reacted with HC2Np in the presence of triethylamine to form complex [6]OTf in 39% yield. Single crystal X-ray diffraction studies of [1](+), [3](+), [4](+), and [6](+) revealed a pseudo-octahedral geometry around the Cr(III) or Co(III) center with the tetraaza-macrocyclic ligand occupying the equatorial plane and the alkynyl- and/or chloro-ligand occupying the apical positions. The absorption spectra of complexes [1](+) and [2](+) display structured d-d bands between 400 and 550 nm, a feature that is absent in the d-d absorption of the Co(III) complexes [3](+)-[6](+). Contrasting emission behaviors were observed: the Cr(III) complexes display metal-centered phosphorescence, while the Co(III) species exhibit ligand-based fluorescence. Time-delayed phosphorescence measurements revealed lifetimes of 447 and 97 mu s for [1](+) and [2](+) at 77 K, respectively, and a room temperature lifetime of 218 mu s for [1](+).