Abstract
Mono- and di-quaternized 4,4′-bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4′-bipyridine-based derivatives are exploited: their redox activity and their electrochromic aptitude. Contemporary materials and compounds encompassing these skeletons as building blocks are often characterized as multifunctional, as their presence often gives rise to interesting phenomena, e.g., various types of chromism. This research trend is acknowledged, and, in this review article, recent examples of multifunctional chromic materials/compounds of this class are presented. Emphasis is placed on solvent-/medium- and environment-responsive 4,4′-bipyridine derivatives. Two important classes of 4,4′-bipyridine-based products with solvatochromic and/or environment-responsive character are reviewed: viologens (i.e., N,N′-disubstituted derivatives) and monoquats (i.e., monosubstituted 4,4′-bipyridine derivatives). The multifunctional nature of these derivatives is analyzed and structure–property relations are discussed in connection to the role of these derivatives in various novel applications.
Highlights
Mono- and di-quaternized 4,40 -bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications
The derivatives of 4,40 -bipyridine have been employed in numerous high-tech applications including molecular motors [2], machines [3,4], and switches [5,6]. 4,40 -Bipyridine is highly abundant in supramolecular chemistry as well, where it mainly serves as an electro- and photo-sensitive building block as well as a bidentate coordinating ligand, very often appearing in covalent organic and metalorganic frameworks (COFs and metal−organic framework (MOF), respectively) [7,8,9]
(1)and andviologen viologenderivatives derivatives synthesized and studied by Benniston al.red synthesized and studied by Benniston et al.etIn red is the dihedral angle between the two pyridine rings of each viologen dication, in black is the is the dihedral angle between the two pyridine rings of each viologen dication, in black is the reduction reductionfor potential for the transformation a viologen dication to the corresponding cation potential the transformation of a viologenofdication to the corresponding radical cation radical and in blue is andabsorption in blue is the absorption maximaofwavelengths of the corresponding the maxima wavelengths the corresponding radical cationsradical
Summary
4,40 -Bipyridine is a heterocyclic compound, which is widely utilized as a building block in numerous materials and compounds [1]. Even though thisEven has only recently started gaining more attention and more attention and there is an increasing number of research articles emphasizing on the alternative there is an increasing number of research articles emphasizing on the alternative uses of 4,4 -bipyridine uses of 4,4′-bipyridine derivatives, no reviews in until this growing areaanup until now. The color of the viologen radical cations in solution is highly affected by solvent polarity as well as the nature of the N-substituents All these effects can lead research to multifunctional systemsterms for the control(blue) of which.
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