We have investigated the use of calix[4]arenes in 3d and 3d/4f chemistry which produced a family of 7 new complexes. These are: [MnIII2MnII2(OH)2(TBC4)2(DMF)6] (1) , the analogous version with C4 (2). [MnIII4GdIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (3), [MnIII4TbIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (4), [MnIII4DyIII4(OH)4(C4)4(NO3)2(DMF)6(H2O)6](OH)2 (5), [CuII9(OH)3(TBC4)3Cl2(DMSO)6](CuICl2)·DMSO (6·DMSO) (6) and [CuII9(OH)3(TBC4)3(NO3)2(DMSO)6](NO3)· DMSO (7·DMSO) (7). We continued with a series of Pseudo Metallocalix[6]arene planar disc complexes : [Ni7(OH)6(L1)6](NO3)2 (8), [Ni7(OH)6(L1)6](NO3)2.2MeOH (9), [Ni7(OH)6(L1)6](NO3)2.3MeNO2 (10), [Ni7(OH)6(L2)6](NO3)2.2MeCN (11), [Zn7(OH)6(L1)6](NO3)2.2MeOH.H2O (12) and [Zn7(OH)6(L1)6](NO3)2.3MeNO2 (13) and in the final part of this thesis we present a family of tetranuclear mixed valent Mn complexes using the tripodal ligand heedH2 : [MnII2MnIV2O2(heed)2(EtOH)6Br2]Br2 (14), [MnII2MnIV2O2(heed)2(H2O)2Cl4] (15), [MnII2MnIV2O2(heed)2(heedH2)2](ClO4)4 (16), [MnII2MnIV2O2(heed)2(MeCN)2(H2O)2(bpy)2](ClO4)4 (17), [MnII2MnIV2O2(heed)2(bpy)2Br4] (18); and the 2-D network of tetranuclear MnII/IV clusters {[MnII2MnIV2O2(heed)2(H2O)2(MeOH)2(dca)2]Br2}n (19). In total nineteen new complexes are reported. Studies of the magnetic properties show that 1 and 2 are SMM’s, whilst complex 3 is an excellent magnetic refrigerant for low-temperature applications and 4 and 5 behave as low-temperature molecular magnets.