1H-MAS-NMR Chemical Shifts in Hydrogen-Bonded Complexes of Chlorophenols (Pentachlorophenol, 2,4,6-Trichlorophenol, 2,6-Dichlorophenol, 3,5-Dichlorophenol, and p-Chlorophenol) and Amine, and H/D Isotope Effects on 1H-MAS-NMR Spectra

Abstract

Chemical shifts (CS) of the 1H nucleus in N···H···O type hydrogen bonds (H-bond) were observed in some complexes between chlorophenols [pentachlorophenol (PCP), 2,4,6-tricholorophenol (TCP), 2,6-dichlorophenol (26DCP), 3,5-dichlorophenol (35DCP), and p-chlorophenol (pCP)] and nitrogen-base (N-Base) by solid-state high-resolution 1H-NMR with the magic-angle-spinning (MAS) method. Employing N-Bases with a wide range of pKa values (0.65–10.75), 1H-MAS-NMR CS values of bridging H atoms in H-bonds were obtained as a function of the N-Base’s pKa. The result showed that the CS values were increased with increasing pKa values in a range of ΔpKa < 0 [ΔpKa = pKa(N-Base) - pKa(chlorophenols)] and decreased when ΔpKa > 2: The maximum CS values was recorded in the PCP (pKa = 5.26)–4-methylpyridine (6.03), TCP (6.59)–imidazole (6.99), 26DCP (7.02)–2-amino-4-methylpyridine (7.38), 35DCP (8.04)–4-dimethylaminopyridine (9.61), and pCP (9.47)–4-dimethylaminopyridine (9.61) complexes. The largest CS value of 18.6 ppm was recorded in TCP–imidazole crystals. In addition, H/D isotope effects on 1H-MAS-NMR spectra were observed in PCP–2-amino-3-methylpyridine. Based on the results of CS simulation using a B3LYP/6-311+G** function, it can be explained that a little changes of the N–H length in H-bond contribute to the H/D isotope shift of the 1H-MAS-NMR peaks.

Synthesis and Characterization of Pt(II) Complexes with Pyridyl Ligands: Elongated Octahedral Ion Pairs and Other Factors Influencing1H NMR Spectra

“… b p K a value from ref . c Estimated from the equation of the line: y = −0.0884 x + 9.0472 (see Supporting Information, Figure S2). d p K a value from ref . e Reported for trans -[Pt­(4-Mepy) 2 Cl 2 ], 8.69 ppm; reported for cis -[Pt­(4-Mepy) 2 Cl 2 ], 8.71 ppm f p K a value from ref . g p K a value from ref . h p K a value from ref . i p K a value from ref . …”

“… a p K a value from ref . b Contains 50 mM [Et 4 N]­Cl. c [Pt­(4-CF 3 py) 4 ]­(BPh 4 ) 2 , 9.01 ppm. d Estimated from the equation of the line: y = −0.0884 x + 9.0472 (see Supporting Information, Figure S2). e p K a value from ref . f p K a value from ref . g Contains 40 mM [Et 4 N]­Cl. h p K a value from ref . i Data collected for [Pt­(4-Me 2 Npy) 4 ]­Cl 2 (without [Et 4 N]­Cl), 8.42 ppm. j [Pt­(4-Me 2 Npy) 4 ]­(BPh 4 ) 2 , 7.88 ppm. k p K a value from ref . l p K a value from ref . …”

Molecular Dynamics of Neutral Polymer Bonding Agent (NPBA) as Revealed by Solid-State NMR Spectroscopy

“…Solid-state NMR (SSNMR) has been proved to be an indispensible technique to investigate the microstructural properties and dynamic behaviors of insoluble and non-crystalized biological systems, carbohydrate complexes and advanced functional materials [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Specifically, an array of techniques, including DIPSHIFT [35,36], 2D WISE [37], SUPER [38], 2 H-NMR [39], REDOR [40,41] and relaxation parameters measurements [42], have been well established to investigate the rigidity or mobility of a variety of functional (bio-)polymers.…”