A new approach to photophysical properties control of main group element π-electron compounds based on the coordination number change

We have explored a new possibility of controlling the properties of the main group element π-electron compounds based on a change in the coordination states of the elements. In a series of trianthryl derivatives of boron, silicon, and phosphorus, various control modes of the properties have been achieved depending on the element. Thus, in the case of the Group 13 boron, the change from tri-coordinate tri(9-anthryl)borane to the corresponding tetra-coordinate fluoroborate results in a significant change in the absorption property associated with the color change from orange to colorless. In the case of the Group 14 silicon, the change from tetra-coordinate tri(9-anthryl)fluorosilane to the corresponding penta-coordinate difluorosilicate causes a significant enhancement in the fluorescence of about 20 fold for the quantum yield. In the case of the Group 15 phosphorus, the fluorescence property is changed in multi-stages from tri-coordinate tri(9-anthryl)phosphine to the corresponding tetra-coordinate phosphonium salt and phosphine oxide, and to the penta-coordinate difluorophosphorane. These results demonstrate the significant potential of the present approach as a new molecular design for the functional main group element compounds.