Feb 18 2010
Organic compounds containing double or triple bonds can pack a powerful punch. By sharing electrons between atoms through a process called pi conjugation, unsaturated molecules often have exceptional photonic and electronic behavior, making them essential components in state-of-the-art products such as polymer light-emitting displays.
One way to boost the usefulness of multiply bonded materials is to add heavy elements other than carbon into organic frameworks. Now, Kohei Tamao and colleagues from the RIKEN Advanced Science Institute in Wako and Kyoto University have developed a size-controllable molecular ring system that enables double bonded silicon–phosphorus units (Si=P) to be securely incorporated into pi conjugated networks1—unlocking previously unseen photo-absorption and emission activity.
Because Si=P bonds are extremely reactive, chemists typically attach them to geometrically large molecules known as bulky ligands that protect the double bonded elements. Unfortunately, most bulky ligands cause the Si=P double bond to twist, disrupting the critical pi conjugation.
Tamao and his team designed a new type of bulky molecule—the so-called ‘Rind’ ligands—to address this rotational problem. Based on a rigid, symmetric skeleton of three fused rings known as s-hydrindacene, Rind groups also contain alkyl side chains that can be tailored in length to control ligand bulkiness.