title: Cucurbit[5]uril-metal complex-induced room-temperature phosphorescence of α-naphthol and β-naphthol.
abstract: Similar to the larger members of the cucurbituril family, such as cucurbit[8]uril (Q[8]), the smallest member, cucurbit[5]uril (Q[5]), can also induce room-temperature phosphorescence (RTP) of α-naphthol (1) and β-naphthol (2). The relationship between the RTP intensity of 1 and 2 and the concentration of Q[5] or Q[8] suggests that the mechanism underlying the Q[5] complex-induced RTP is different from that of the Q[8]-induced RTP for these luminophores. The crystal structures of 1-Q[5]-KI, 2-Q[5]-KI, 1-Q[5]-TlNO(3), and 2-Q[5]-TlNO(3) systems show that in each case Q[5] and the respective metal ions, K(+) or Tl(+), form infinite ···Q[5]-M(+)-Q[5]-M(+)··· chains that surround the luminophores. Although these tube- or wall-like structures are likely destroyed in solution, the key interaction between the convex-shaped outer walls of Q[5] and the plane of the aromatic naphthols, via π···π stacking and C-H···π interactions, is postulated to be essentially maintained leading to a microenvironment that holds the luminophore and the heavy atom perturber together; such a model is supported by the observed Q[5] complex-induced RTP of the above naphthols. With respect to this, a high Q[5]/luminophore concentration was employed in an endeavour to promote the formation of π···π stacking and C-H···π interactions similar to those observed in the crystal structures of the 1- or 2-Q[5]-K(+) and -Tl(+) systems. In keeping with the proposed model, the RTP of each system is quenched when Q[5] is replaced by the alkyl-substituted Q[5] derivatives, decamethylQ[5] and pentacyclohexanoQ[5]. This is in agreement with the substituent groups on the surface of the metal-bond Q[5] obstructing the naphthol molecule from accessing the convex glycouril backbone of Q[5].
authors.affiliation: Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, People's Republic of China.
authors.forename: Zhong-Wei
authors.initials: ZW
authors.lastname: Gao
authors.forename: Xing
authors.initials: X
authors.lastname: Feng
authors.forename: Lan
authors.initials: L
authors.lastname: Mu
authors.forename: Xin-Long
authors.initials: XL
authors.lastname: Ni
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Liang
authors.forename: Sai-Feng
authors.initials: SF
authors.lastname: Xue
authors.forename: Zhu
authors.initials: Z
authors.lastname: Tao
authors.forename: Xi
authors.initials: X
authors.lastname: Zeng
authors.forename: Bodgan E
authors.initials: BE
authors.lastname: Chapman
authors.forename: Philip W
authors.initials: PW
authors.lastname: Kuchel
authors.forename: Leonard F
authors.initials: LF
authors.lastname: Lindoy
authors.forename: Gang
authors.initials: G
authors.lastname: Wei
mesh_terms: D001952:Bridged-Ring Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D009284:Naphthols / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011193:Potassium Iodide / Q000737:chemistry*; D013696:Temperature; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
chemical_list: D001952:Bridged-Ring Compounds; D007093:Imidazoles; D009284:Naphthols; D009942:Organometallic Compounds; D011193:Potassium Iodide; C523802:cucurbit(5)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils; C029350:1-naphthol; C028405:2-naphthol