Structure of bTbK (a) and modified bTurea with a PEG chain(b), obtained via DFT. The g-tensors and dipolar coupling are represented schematically, (the axis length is proportional to the principal axis frame tensor value). In blue and yellow, the g-tensor of electron spin a and b, respectively. The colour coding for the atoms is: black corresponds to carbon (C), red to oxygen (O), blue to nitrogen (N), and grey to hydrogen (H)). The structures have been generated with a home-written Matlab code.