text: After a brief apprenticeship in applying standard versions of ligand field modelling to transition metal complexes, tackling  single-crystal polarized spectra and magnetic anisotropy of Ni(II) and Co(II) complexes in the less usual five-coordination states, Werner Urland conceived his own "trademark" devising a ligand-field potential for f electrons in the frame of Angular Overlap Model.
  Immediate applications clarified the meaning of the parameters, taking rare-earth hydroxides and chlorides as case studies. Many papers developed in this domain were single authored, marking the original perspective of Werner Urland. Briefly, describing the situation of Ligand field theory, practically equivalent to Crystal Field Theory pointing that this method is more popular, often invoked in qualitative respects, for transition metal systems (coordination and solid phase compounds)  while for f-elements (lanthanide and actinide compounds) it is regarded as a rather specialized field, due to somewhat more complicated technical stances. A conceptual drawback is the lack of chemical intuitiveness of the parameters of classical ligand field theories. There are several conventions, such as Wybourne or Stevens parameterizations    An alternate offer was identified in the Angular Overlap Model basically developed for d-type transition metal systems   It is the merit of Werner Urland for stating the AOM version for f-type compounds, advocating for it by systematic applications acting as proof for the validity of this approach. 
  The theoretical activity was complemented by involvement in synthetic coordination chemistry, producing new coordination compounds taken as relevant new case studies for ligand field interpretation of magnetic properties. A series consisting in individual octahedral units [LnCl], is interesting by the intrinsic simplicity of these complexes, once is known that lanthanide complexes are usually adopting higher coordination numbers, the hexa-coordination being enforced  mostly by the doping regime, in solid lattices, such as elpasolites (a variety of Halide minerals  with ABMXstoichiometry). The magnetic properties of [LnCl] complexes (with pyridinium counter ions) were analysed in the non-trivial details of the causal role of the ligand field effects.  In the same spirit, a detailed attention was devoted to the relatively simple lanthanide pentakis nitrato complexes, starting from the synthesis stage   continued into the instrumental and theoretical characterization. The Electron paramagnetic resonance (EPR) spectra of the pentakis nitrato ytterbate(III), [Yb(NO)]    was recorded and modelled, the ligand field treatment being based also on advanced neutron spectroscopy measurements.
  A peculiar manifestation, discovered in the light of the developed methodologies, was the first report of level crossing in ligand field diagrams, tuned by external pressure.
  A systematic attention was devoted to the magnetism determined by lanthanide ions in solid compounds like the ternary oxides,  CsLnO  or CsMLnX elpasolite type systems, with various combination of (M = Na, K, Rb) alkaline metal ions and (X=F, Cl, Br) halides, for several Ln(III) rare earth cases. Werner Urland proved the ligand field as the determinant for the pattern of magnetic susceptibility dependences on temperature, often mistakenly attributed to inter-center exchange coupling.
  A distinct branch of investigation concerned the unusual ferromagnetic Gd(III)-Gd(III) exchange coupling recorded in newly synthesized homo-polynuclear complexes of gadolinium with various carboxylates (acetate, fluoro- and chloro- substituted acetate) as bridging ligand.