Here we propose measurements on a unique, newly synthesized series of coordination polymers based on chains of Cu2+ ions. These have been designed with the intention of determining the precise factors promoting magnetic exchange via halogen ions. It is hoped that the insight provided by this study will allow the use of halogen-based structural motifs in building molecular systems with controlled interaction strengths through designated exchange pathways. The new series forming the basis of this proposal has the formula CuX2(3-ClPy)2 where X =Cl, Br and F. Crucially, these materials represent the first isostructural series of halogen bibridged copper complexes and affords a unique opportunity to quantify the tuning of the magnetic interactions that occurs upon substitution of different halogens. We will determine the ordering temperatures of these materials and probe magnetic excitations.