title: Coordination-driven self-assembly of 2D-metallamacrocycles using a new carbazole-based dipyridyl donor: synthesis, characterization, and C60 binding study.
abstract: A new carbazole-based 90° dipyridyl donor 3,6-di(4-pyridylethynyl)carbazole (L) containing carbazole-ethynyl functionality is synthesized in reasonable yield using the Sonagashira coupling reaction. Multinuclear NMR, electrospray ionization-mass spectrometry (ESI-MS), including single crystal X-ray diffraction analysis characterized this 90° building unit. The stoichiometry combination of L with several Pd(II)/Pt(II)-based 90° acceptors (1a-1d) yielded [2 + 2] self-assembled metallacycles (2a-2d) under mild conditions in quantitative yields [1a = cis-(dppf)Pd(OTf)(2); 1b = cis-(dppf)Pt(OTf)(2); 1c = cis-(tmen)Pd(NO(3))(2); 1d = 3,6-bis{trans-Pt(C≡C)(PEt(3))(2)(NO(3))}carbazole]. All these macrocycles were characterized by various spectroscopic techniques, and the molecular structure of 2a was unambiguously determined by single crystal X-ray diffraction analysis. Incorporation of ethynyl functionality to the carbazole backbone causes the resulted macrocycles (2a-2d) to be π-electron rich and thereby exhibit strong emission characteristics. The macrocycle 2a has a large internal concave aromatic surface. The fluorescence quenching study suggests that 2a forms a ~1:1 complex with C(60) with a high association constant of K(sv) = 1.0 × 10(5) M(-1).
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560 012, India.
authors.forename: Sankarasekaran
authors.initials: S
authors.lastname: Shanmugaraju
authors.forename: Vaishali
authors.initials: V
authors.lastname: Vajpayee
authors.forename: Sunmi
authors.initials: S
authors.lastname: Lee
authors.forename: Ki-Whan
authors.initials: KW
authors.lastname: Chi
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Stang
authors.forename: Partha Sarathi
authors.initials: PS
authors.lastname: Mukherjee