An NMR analysis of N-phenyl polyiminomethylene analogs accompanied by the development of an apodization function

Lynne Renee Spencer, University of Rhode Island


An apodization function, the Sinc Reducing TRAF function (S-TRAF), was developed which removes sinc ripple distortions with only minor losses in line width (LW) and signal-to-noise (S/N) on heavily truncated NMR time domain signals. S-TRAF is a modified version of the TRAF for sensitivity function. Its performance is superior to the TRAF for ripple removal when acquisition times (AT) are less than 0.8 T$\sb2$*; LW and S/N results from application of S-TRAF rival those observed for TRAF for AT from 0.5 T$\sb2$* to T$\sb2$* and are only slightly worse at lower AT. The extent of ripple irradication resulting from use of S-TRAF rivals that observed with the 'Ultimate Ripple-Free Resolution Enhancement' function (URFRE) for AT as low as 0.5 T$\sb2$*. Additionally, S-TRAF use broadens LW less than application of URFRE at low AT.^ Five analogs of N-phenyl polyiminomethylene (N-$\varphi$-PIM) (N-phenyl benzophenone imine (1), N,N-diphenyl benzyl diimine (2), 1,3-dibenzoylbenzylidenimine (3), 2,3-bis(phenylimino)-1,3-diphenyl-1,2,3-propantrione (4), and Tris(phenylimino)-1,3-diphenyl-1,2,3-propantrione (5)) have been analyzed by solution NMR spectroscopy. $\sp1$H and $\sp{13}$C chemical shift assignments were made on all five compounds and $\sp{15}$N chemical shifts were assigned on 4 and 5. $\rm J(\sp{15}N\sp{13}C)$ and $\rm J(\sp{15}N\sp{15}N)$ couplings were observed and assigned using selective irradiation techniques. Two compounds (4 and 5) show vicinal $\sp{15}$N-$\sp{15}$N couplings of 2.7 Hz. Two conformations of analog 4 are observed in solution at ambient temperature. Results indicate only one conformation is present in solution for each of the other four analogs. $\rm \sp2J(\sp{15}N\sp{13}C)$ are used to determine qualitative conformations for the major form of 4 and 5. The orientation of 5 is in good agreement with recent theoretical studies in the literature. The results indicate $\sp{15}$N chemical shifts are promising geometric probes for the structure of PIM polymers in solution. This is based on the relationship of deshielding/shielding of $\sp{15}$N shifts to the extent of n-$\pi$ delocalization in the molecule. ^

Subject Area

Chemistry, Analytical|Chemistry, Polymer

Recommended Citation

Lynne Renee Spencer, "An NMR analysis of N-phenyl polyiminomethylene analogs accompanied by the development of an apodization function" (1997). Dissertations and Master's Theses (Campus Access). Paper AAI9812225.