Self-assembly of Er( iii ) ions with octacyanidotungstate( v ) in the presence of pure N , N -dimethylacetamide (dma) resulted in the formation of one-dimensional zigzag chain {Er III (dma) 5 W V (CN) 8 } n ( 1 ). Coordination polymer 1 crystallizes in the non-centrosymmetric space group P 2 1 and it exhibits second harmonic generation (SHG) effect with SH susceptibility of 5.8 × 10 −11 esu. Interestingly, the treatment of 1 with small amount of water results in the generation of another complex salt Er III (dma) 5 (H 2 O) 2 ·W V (CN) 8 ·dma·H 2 O ( 2 ) which crystallizes in centrosymmetric space groups of P 2 1 / n , disqualifying the occurrence of SHG phenomenon. On the other hand, the elimination of cyanido-bridges and formation of seven-coordinated erbium( iii ) centre resulted in magnetic field induced single molecule magnet (SMM) behaviour with effective energy barrier of 28.6(3) K for 2 . Finally, self-assembly of Er( iii ) with octacyanidotungstate( v ) in water/dma mixture gave a complex salt Er III (dma) 4 (H 2 O) 3 ·W V (CN) 8 ·dma·3H 2 O ( 3 ) similar to 2 . Dynamic magnetic studies reveal that 3 is also showing slow magnetic relaxation, however, the substitution of single dma by water molecule induces the change in the local geometry of Er( iii ) centre leading to weak SMM properties for 3 . Studies of {Er(dma) 5 W(CN) 8 } n ( 1 ) showing nonlinear optical effect of second harmonic generation, and Er(dma) 5 (H 2 O) 2 ·W(CN) 8 ·dma·H 2 O ( 2 ) and Er(dma) 4 (H 2 O) 3 ·W(CN) 8 ·dma·3H 2 O ( 3 ) revealing field-induced single molecule magnet behavior.