H/D Isotope Effects on 1H-NMR Chemical Shifts in Cyclic Heterodimers and Heterotrimers of Phosphinic and Phosphoric Acids.

Hydrogen-bonded heterocomplexes formed by POOH-containing acids (diphenylphosphoric 1, dimethylphosphoric 2, diphenylphosphinic 3, and dimethylphosphinic 4) are studied by the low-temperature (100 K) 1H-NMR and 31P-NMR using liquefied gases CDF3/CDF2Cl as a solvent. Formation of cyclic dimers and cyclic trimers consisting of molecules of two different acids is confirmed by the analysis of vicinal H/D isotope effects (changes in the bridging proton chemical shift, δH, after the deuteration of a neighboring H-bond). Acids 1 and 4 (or 1 and 3) form heterotrimers with very strong (short) H-bonds (δH ca. 17 ppm). While in the case of all heterotrimers the H-bonds are cyclically arranged head-to-tail, ···O=P-O-H···O=P-O-H···, and thus their cooperative coupling is expected, the signs of vicinal H/D isotope effects indicate an effective anticooperativity, presumably due to steric factors: when one of the H-bonds is elongated upon deuteration, the structure of the heterotrimer adjusts by shortening the neighboring hydrogen bonds. We also demonstrate the formation of cyclic tetramers: in the case of acids 1 and 4 the structure has alternating molecules of 1 and 4 in the cycle, while in case of acids 1 and 3 the cycle has two molecules of 1 followed by two molecules of 3.

. Parts of 31 P NMR spectrum of a mixture of acids 2 and 3.
3 Figure S3. The low-field part of 1 H NMR spectrum of a mixture of acids 2 and 4. 4 Figure S4. Parts of 31 P NMR spectrum of a mixture of acids 2 and 4. 5 Figure S5. The low-field part of 1 H NMR spectrum of a mixture of acids 3 and 4. 6 Figure S6. Parts of 31 P NMR spectrum of a mixture of acids 3 and 4. 7 Figure S7. Probabilities of various isotopologs and relative intensities of their signals as a function of deuteration ratio x D .
8 Figure S8. The low-field part of 1 H NMR spectrum of a mixture of partially deuterated acids 2 and 3.
9 Figure S9. The low-field parts of 1 H NMR spectra of a mixture of partially deuterated acids 3 and 4 at various degrees of deuteration.
10 Table S1. 31 P NMR chemical shifts of homodimers and heterodimers of acids 1-4. 11 Table S2. 31 P NMR chemical shifts of homotrimers and heterotrimers of acids 1-4. 12 Figure S10. The analysis of H/D fractionation factors for a mixture of partially deuterated acids 2 and 3.
13 Table S3. The deuteration ratios of individual hydrogen bonds for the sample of a mixture of partially deuterated acids 2 and 3.
For visual clarify the signals in the experimental spectrum and the computed sub-spectra are color coded.  Figure S2. The parts of 31 P NMR spectrum of the sample containing acids 2 and 3 (1.8:1) in CDF 3 /CDF 2 Cl at 100 K. The experimental spectrum is deconvoluted into the sub-spectra arising from self-associated of 2 and two heterotrimers, 2-3-2 and 3-2-3. The self-associates of 3 are not formed, while the signals of heterodimer 2-3 are not detected due to their low intensity. For visual clarify the signals in the experimental spectrum and the computed sub-spectra are color coded.   (1:1.4) in CDF 3 /CDF 2 Cl at 100 K. The experimental spectrum is deconvoluted into the subspectra arising from self-associated of 4, heterodimer 3-4 and two heterotrimers, 3-4-3 and 4-3-4.
For visual clarify the signals in the experimental spectrum and the computed sub-spectra are color coded.    2001, 379, 191-193.]. cthe diphenylphosphinic acid 3 is poorly soluble in CDF 3 /CDF 2 Cl and does not form selfassociates in a detectable amount dn.d.not detected. en.m.not measured.   2001, 379, 191-193.]. cthe diphenylphosphinic acid 3 is poorly soluble in CDF 3 /CDF 2 Cl and does not form selfassociates in a detectable amount dn.d.not detected.  Table S3.
Note: the H/D fractionation factors are defined with respect to a standard/reference, which is usually water. In our case the fractionation factors were calculated either with respect to one of the complexes (green labels in Figure S10) or within a selected pair of complexes (red labels). It has to be mentioned that for many other samples the changes of deuteration ratios x D between individual complexes are either too small or lie within the experimental error. Table S3. The deuteration ratios of individual hydrogen bonds for the sample of a mixture of partially deuterated acids 2 and 3 (see 1 H NMR spectrum in Figure S8). Note that intensities of some isotopologs are too small to reliably measure the deuteration ratio (this is why only one signal of heterotrimer 3-2-3 was analyzed).