Asymmetrically Substituted and π-Conjugated 2,2′-Bipyridine Derivatives: Synthesis, Spectroscopy, Computation, and Crystallography

Abstract

A new series of monosubstituted styryl- and bistyryl-2,2'-bipyridine luminophores (compounds 16-23) have been synthesized via Horner-Wadsworth-Emmons reaction involving a monophosphonate and donor aromatic aldehydes. In the title chromophores, the amino donors are varied between acyclic and cyclic while the alkoxy donors are varied in terms of their number and position. The absorption maxima of these chromophores shift predominantly due to intramolecular charge transfer (ICT) between different donor and acceptor moieties. The title donor-acceptor molecules exhibit intense fluorescence in solution at room temperature, and their emissive behavior has been found to be highly sensitive to solvent polarity. The fluorescence spectra and quantum yields of all the chromophores were recorded in four different solvent media, and the chromophores 16, 17, 19, and 21 exhibit fluorescence in the solid state too. The influence of the nature and position of the donor functionalities in the conjugated backbone of the bipyridine moiety on the electronic absorption properties of the title chromophores (16-23) has been demonstrated, which has further been corroborated by DFT and TD-DFT computation both in gas phase and in solution phase. The crystal structure of compound 18 has been described as a representative member of the family (16-23).

Spectroscopic, structural and DFT studies of luminescent Pt(II) and Ag(I) complexes with an asymmetric 2,2′-bipyridine chelating ligand

“…It has previously been shown that the presence of substituents at 5,5'-positions of 2,2'-bipyridine causes a significant red-shift of the emission maximum akin to that of the protonated ligand [8]. The main interactions in these molecules occur by an intramolecular charge-transfer (ICT) between the donor (D) and acceptor (A) functionalities, thereby tuning the optical properties [9]. The bpy derivatives are very promising candidates as a fluorescent probe, a property that is associated with the orbital energy of the lowest unoccupied molecular orbital (LUMO) of pyridine [9].…”

“…The main interactions in these molecules occur by an intramolecular charge-transfer (ICT) between the donor (D) and acceptor (A) functionalities, thereby tuning the optical properties [9]. The bpy derivatives are very promising candidates as a fluorescent probe, a property that is associated with the orbital energy of the lowest unoccupied molecular orbital (LUMO) of pyridine [9]. As both a σ-donor and π-acceptor ligand, 2,2′-bipyridine derivatives form very stable metal complexes due to the formation of a five-membered ring [10].…”

Functional Molecular System of Bis(pyrazolyl)pyridine Derivatives: Photophysics, Spectroscopy, Computation, and Ion Sensing

“…26 We have also reported a series of asymmetrically substituted and π-conjugated 2,2′-bipyridine derivatives including their photophysics and computational studies. 27 Last several years, in our laboratory, we have been exploring diverse inorganic and organic systems that can be described as functional materials. 28−30 As a part of our recent research on exploring functional materials, we have recently developed interests in fluorescent chemosensors and reported our first success in selective sensing of Fe 3+ ion and IO 4 – ion by a metallocycle host.…”

“…We have also performed density functional theory (DFT) calculations to corroborate the UV−visible and ■ RESULTS AND DISCUSSION Synthesis. The 2,6-bis(pyrazolyl)-4-bromomethyl pyridine precursor IK-1 (see Chart 1 for the structural representation of IK-1) 46 and the required appropriate N,N-dialkylated-and pyrrolidine-substituted aldehydes S 1c−7c 26,27 (see Scheme S1, Supporting Information for syntheses and structural drawings of S 1c−7c ) along with their precursors were synthesized according to the literature procedures in good yields (see Schemes S1 and S2 in the Supporting Information). Compound IK-2 (phosphate derivative, see Chart 1) was synthesized by Arbuzov reaction of compound IK-1 with Crystal Structure Description and Discussion.…”

“…The singlet state undergoes preferable stabilization in more polar solvents via solvent reorganization, which can be realized by large Stokes shifts of the fluorescence emission. − Numerous π-conjugated systems that can be described as functional materials are particularly important to the development of organic light-emitting diodes, electrogenerated chemiluminescence, dye-sensitized solar cells, and fluorescent sensors. − Some years ago, we have established a series of 4,4′-π-conjugated-2,2′-bipyridine chromophores and investigated their photophysical and thermal properties . We have also reported a series of asymmetrically substituted and π-conjugated 2,2′-bipyridine derivatives including their photophysics and computational studies . Last several years, in our laboratory, we have been exploring diverse inorganic and organic systems that can be described as functional materials. − As a part of our recent research on exploring functional materials, we have recently developed interests in fluorescent chemosensors and reported our first success in selective sensing of Fe 3+ ion and IO 4 – ion by a metallocycle host .…”