Theoretical calculations of the chemical shifts of cyclo[n]phosphazenes for n = 2, 3, 4 and 5 (X₂PN)_n with X = CH₃, F, Cl and Br: the effect of relativistic corrections

Abstract

Di, tri, tetra and pentacyclophosphazenes substituted on the phosphorus atoms by CH₃, F, Cl and Br atoms corresponding to (X₂PN)_n structures have been studied theoretically at the B3LYP/6-311++G(d,p) level. After a brief discussion of their geometries comparing them to those of the conjugated carbocycles, (CH)_n, of the same size, the absolute shieldings calculated with the GIAO and ZORA approximations will be reported. For the Cl and mainly for the Br substituted cyclo[n]-phosphazenes, relativistic corrections are absolutely necessary for ³¹P and useful for ¹⁵N chemical shifts.

GRAPHICAL ABSTRACT

Keywords:

• Cyclo[n]phosphazenes
• NMR
• GIAO
• ZORA
• Free-Wilson

Acknowledgments

Thanks are also given to the CTI (CSIC) for their continued computational support.

Additional information

Funding

This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades (Project PGC2018-094644-B-C22) and Dirección General de Investigación en Innovación de la Comunidad de Madrid (PS2018/EMT-4329 AIRTEC-CM).