Abstract
Cyclodextrins (CDs) have drawn a lot of attention from the scientific communities as a model system for host–guest chemistry and also due to its variety of applications in the pharmaceutical, cosmetic, food, textile, separation science, and essential oil industries. The formation of the inclusion complexes enables these applications in the condensed phases, which have been confirmed by nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography, and other methodologies. The advent of soft ionization techniques that can transfer the solution-phase noncovalent complexes to the gas phase has allowed for extensive examination of these complexes and provides valuable insight into the principles governing the formation of gaseous noncovalent complexes. As for the CDs’ host–guest chemistry in the gas phase, there has been a controversial issue as to whether noncovalent complexes are inclusion conformers reflecting the solution-phase structure of the complex or not. In this review, the basic principles governing CD’s host–guest complex formation will be described. Applications and structures of CDs in the condensed phases will also be presented. More importantly, the experimental and theoretical evidence supporting the two opposing views for the CD–guest structures in the gas phase will be intensively reviewed. These include data obtained via mass spectrometry, ion mobility measurements, infrared multiphoton dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations.
Highlights
Cyclodextrins (CDs) are macrocyclic oligosaccharides commonly composed of six, seven, or eight d-glucopyranoside units linked in α-(1,4) bonds (Figure 1), denoted as α-CD, β-CD, and γ-CD, respectively
Thanks in part to nuclear magnetic resonance (NMR) analysis of the associated solutions, the idea of the CD complexes in electrospray ionization mass spectrometry (ESI-MS) studies was widely accepted without any rigorous scrutiny, even though inclusion CD complexes in ESI-MS studies was widely accepted without any rigorous scrutiny, even the ionization/transfer process can change complex structures [150,151,152], until Cunniff and Vouros highlighted the possibility of false-positive detection in the ESI-MS studies [141]
Thanks incorporated to its broad-scale applicability, Ion-mobility spectrometry (IMS) has evolved into instruments distinct branches, drift time into state-of-the-art commercial mass spectrometry to simplifynamely, the product matrix ofhigh-field the complex mixtures obtained from various biological samples tandemand masstrapped
Summary
Cyclodextrins (CDs) are macrocyclic oligosaccharides commonly composed of six, seven, or eight d-glucopyranoside units linked in α-(1,4) bonds (Figure 1), denoted as α-CD, β-CD, and γ-CD, respectively. These structural characteristics facilitate the use of CDs in a wide range of chemical and analytical applications, namely, in sample preparation [8,9,10], purification [11,12,13,14,15], spectroscopic analysis ability to selectively form noncovalent host–guest complexes with small molecules or enantiomeric as molecular booster agentsand for enhancing analyte sensitivity during luminescence and fluorescence species [1,2,3][16,17], due to chiral recognition processes, respectively. The lock and key model, which was first suggested by Emil Fisher, attributes the specific binding of enzyme and substrate to the optimal geometric fit between them [32] This model is especially useful for explaining the recognition of guest molecules lacking notable interaction parts in the CD complex system [24]. Springer Nature: Springer International Publishing AG, Cyclodextrin Fundamentals, Reactivity and Analysis by Crini et al, Reference [3], COPYRIGHT (2018)
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