Synthesis, photophysical and electrochemical properties, and protein-binding studies of luminescent cyclometalated iridium(III) bipyridine estradiol conjugates.
A new series of luminescent cyclometalated iridium(III) bipyridine estradiol conjugates [Ir(N-C)2(N-N)](PF6) (N-N = 5-(4-(17alpha-ethynylestradiolyl)phenyl)-2,2'-bipyridine, bpy-est, HN-C = 2-phenylpyridine, Hppy (1 a), 1-phenylpyrazole, Hppz (2 a), 7,8-benzoquinoline, Hbzq (3 a), 2-phenylquinoline, Hpq (4 a), 2-((1,1'-biphenyl)-4-yl)benzothiazole, Hbsb (5 a); N-N = 4-(N-(6-(4-(17alpha-ethynylestradiolyl)benzoylamino)hexyl)aminocarbonyl)-4'-methyl-2,2'-bipyridine, bpy-C6-est, HN-C = Hppy (1 b), Hppz (2 b), Hbzq (3 b), Hpq (4 b), Hbsb (5 b)) was synthesized, characterized, and their photophysical and electrochemical properties studied. Upon photoexcitation, all the complexes displayed intense and long-lived emission in fluid solutions at 298 K and in low-temperature glass. The emission of complexes 1 a-3 a and 1 b-3 b was assigned to a triplet metal-to-ligand charge-transfer ((3)MLCT) (dpi(Ir)-->pi*(bpy-est and N-C-)) state mixed with some triplet intraligand ((3)IL) (pi-->pi*) (N-C- and N-N) character. However, the emissive states of the pq- and bsb- complexes 4 a, 4 b, 5 a, and 5 b showed substantial (3)IL (pi-->pi*) (pq-/bsb-) character. The lipophilicity of all the complexes was determined by reversed-phase HPLC. Upon binding to estrogen receptor alpha, all of these iridium(III) estradiol conjugates exhibited emission enhancement and lifetime extension, rendering them a novel series of luminescent probes for this receptor.
Lo
Kenneth Kam-Wing
KK
Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People's Republic of China. bhkenlo@cityu.edu.hk
Zhang
Kenneth Yin
KY
Chung
Chi-Keung
CK
Kwok
Karen Ying
KY
D015082:2,2'-Dipyridyl / Q000138:chemical synthesis* / Q000737:chemistry*; D004563:Electrochemistry; D004958:Estradiol / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry; D007495:Iridium / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011485:Protein Binding
D009942:Organometallic Compounds; D007495:Iridium; D004958:Estradiol; D015082:2,2'-Dipyridyl