The novel one-dimensional coordination polymer [Cd(ADC)(H 2 O) 3 ] H 2 O, where ADC 2-) acetylenedicarboxylate dianion, was synthesized and characterized by single-crystal X-ray diffraction. The titled compound crystallizes in the monoclinic system, P2 1 /n, a ) 6.908(1) Å, b ) 7.946(1) Å, c ) 16.390(1) Å, β ) 100.21(1)°, V ) 885.4(2) Å 3 , and Z ) 4. The structure is made up of metal-organic chains linked by hydrogen bonds to form channels along the b axis. The carbon-carbon triple bonds are in close proximity (3.27 Å) along the a axis. This induces, upon heating, polymerization with formation of conjugated polycarboxylic chains. Detailed EPR studies have been performed in order to understand the polymerization process.