Cooperative magnetic interactions have been observed in α‐[MnPc][TCNE], which results from the reaction of manganese phthalocyanine with tetracyanoethylene. This is the latest in a series of molecule based materials found to exibit such unusual magnetic behaviour. The α polymorph displays very strong magnetic coupling, while the coupling in β‐[MnPc][TCNE] is much weeker. The IR data suggest that the behaviour of the α polymorph is unlikely to be unique among the metallomacrocyclic electron‐transfer complexes. It is proposed that uniformity of the one0‐dimensional chains in α‐[MnPc][TCNE] and the corresponding lack of uniformity of those in the β polymorph may give rise to the difference in behaviour.

Nitroprussides of divalent transition metals form a family of microporous molecular materials. Their properties in this sense depend on the transition metal cation involved and also on the preparative method, which determine their crystal structures. The stable phases of this family of materials belong to one of the following crystal structures: orthorhombic (Pnma) (Mn 2+ , Fe 2+ , Cu 2+ , Zn 2+ , and Cd 2+ ), cubic (Fm3m) (Co 2+ and Ni 2+ ), and orthorhombic (Amm2) (Cu 2+ ). These materials are stable up to above 160°C, while their dehydration takes place around 100°C. On dehydration, Amm2 copper complex changes into a tetragonal (I4mm) phase. The microporous nature of these materials is discussed according to their crystal structure and correlating structural and adsorption data. The accessibility to the pore system was evaluated through adsorption of H 2 O, CO 2 , and N 2 . Pores of both orthorhombic and cubic structures are accessible to H 2 O and CO 2 in experiments carried out at 23 and 0°C, respectively; however, they are inaccessible to N 2 at -196°C. This behavior is discussed as related to the large polarizing power of the nitrosyl (NO) ligand which distorts the local environment of the iron atom and reduces the effective window cross section. The small pores of tetragonal copper nitroprusside were inaccessible to the adsorbates used.

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