Self-assembly of a chloro-bridged half-sandwich p-cymene ruthenium(II) complex [Ru2 (l-Cl2)(g6-pcymene) 2Cl2] 1 with linear ditopic donor [L; trans-1,2-bis(4- pyridyl)ethylene] in presence of 2 eq. AgNO3 in CH3CN yielded a chloro-bridged molecular rectangle 2. The rectangle 2 was isolated as nitrate salt in high yield (90 %) and characterized by infra-red, 1H NMR spectroscopy including ESI-MS analyses. Molecular structure of 2 was determined by single crystal X-ray diffraction study The diffraction analysis shows that 2 adopts a tetranuclear rectangular geometry with the dimensions of 5.51 Å 9 13.29 Å and forming an infinite supramolecular chain with large internal porosity arising through multiple p-p and CH-p interactions between the adjacent rectangles. Furthermore, rectangle 2 is used as selective receptor for phenolic-nitroaromatic compounds such as picric acid, dinitrophenol and nitrophenol. © The National Academy of Sciences, India 2014.