Agradecimentos: RMG acknowledges the support provided by the CLAF-ICTP program for his PhD studies. ER is grateful for the support provided by CLAF-ICTP for carrying out research activities on molecular materials. The authors thank C Vazquez-Ramos from IIM-UNAM for TG data acquisition. The support from FAPESP and CNPq (Brazilian agencies) is acknowledged Ver menos

Abstract: The magnetic interaction between adjacent manganese atoms through aquo double bridges in Mn-2[M(CN)(6)] center dot xH(2)O where x = 8 and 2 and M= Fe, Ru, Os, was studied. Through these bridges a relatively weak antiferromagnetic interaction is established with an estimated Curie-Weiss temperature, vertical bar theta(CW)vertical bar, close to 4 K and a super exchange constant, vertical bar J vertical bar, of 0.27 cm(-1). When these materials are dehydrated the antiferromagnetic interaction between the Mn atoms undergoes a dramatic increase, with estimated values for vertical bar theta(CW)vertical bar and vertical bar J vertical bar of 61 K and 4.11 cm(-1), respectively. Such reinforcement in the magnetic interaction is accompanied by a shift of 32 cm(-1) for the. (CN) vibration towards the low frequency region while for the iron compound the Mossbauer spectrum, initially a single line, becomes a quadrupole splitting doublet of relatively low isomer shift (delta) value. The Curie constant of the involved Mn atoms shows a negative correlation with the observed shifts in. (CN) and d on dehydration. From the observed magnetic behaviour and the spectroscopic data a double coordination of an N end of the CN ligand to two Mn atoms is proposed. Such strong magnetic interaction through the N atom of the CN ligand could be used as a prototypical bridge to obtain high T-c molecular magnets Ver menos