An NMR crystallography study of the hemihydrate of 2′, 3′-O-isopropylidineguanosine

G.N Manjunatha Reddy,Daniel S Cook,Dinu Iuga,Richard I Walton,Andrew Marsh,Steven P Brown

doi:10.1016/j.ssnmr.2015.01.001

G.N Manjunatha Reddy, Daniel S Cook + Show 4 more

Open Access

https://doi.org/10.1016/j.ssnmr.2015.01.001

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Abstract

An NMR crystallography study of the hemihydrate of 2′, 3′-O-isopropylidineguanosine (Gace) is presented, together with powder X-ray diffraction and thermogravimetric analysis. 1H double-quantum and 14N–1H HMQC spectra recorded at 850MHz and 75kHz MAS (using a JEOL 1mm probe) are presented together with a 1H–13C refocused INEPT spectrum recorded at 500MHz and 12.5kHz MAS using eDUMBO-1221H homonuclear decoupling. NMR chemical shieldings are calculated using the GIPAW (gauge-including projector augmented wave) method; good two-dimensional agreement between calculation and experiment is observed for 13C and 1H chemical shifts for directly bonded CH and CH3 peaks. There are two Gace molecules in the asymmetric unit cell: differences in specific 1H chemical shifts are rationalised in terms of the strength of CH-π and intermolecular hydrogen bonding interactions.

Highlights

The collaborative computational project for NMR crystallography (CCP-NC, www.ccpnc.ac.uk) defines NMR crystallography as the combined use of experimental NMR and computation to provide new insight, with atomic resolution, into structure, disorder and dynamics in the solid state
Notably by Harris [1,2] and Emsley [3], NMR crystallography of solid-state structures adopted by organic molecules is becoming a vibrant research area
This paper considers 20, 30-O-isopropylidineguanosine; using the notation in Ref. [25], this is referred to as Gace

Summary

Introduction

Augmented wave) method have been performed for a wide variety of organic solids [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]. [25], this is referred to as Gace (i.e., for guanosine acetonide). Such guanosine derivatives are of interest because of the rich supramolecular chemistry exhibited in organic solutions, on surfaces and in the solid state [36,37,38], with self assembly being characterised by 23Na, 39K and 87Rb [39,40,41,42,43] as well as 1H, 13C, 14N and 15N [25,44,45] solid-state NMR.

Experimental and computational details

PXRD and TGA

Experimental and GIPAW calculated 13C chemical shifts

Summary