Guanine DNA quadruplexes are interesting and important biological objects because they represent potential targets for regulatory drugs. Their use as building blocks for biomaterial applications is also being investigated. This contribution reports the in silico design of artificial building blocks derived from xanthine. Methods of quantum chemistry were used to evaluate the properties of xanthine structures relative to those containing guanine, the natural reference used. Tailoring the xanthine core showed that the base stacking and the ion coordination were significantly enhanced in the designed systems, while the ion-transport properties were not affected. Our study suggests that the 9-deaza-8-haloxanthine bases (where the halogen is fluorine or chlorine) are highly promising candidates for the development of artificial quadruplexes and quadruplex-active ligands.