In this paper, a novel topological index, named M-index, is introduced based on expanded form of the Wiener matrix. For constructing this index the atomic characteristics and the interaction of the vertices in a molecule are taken into account. The usefulness of the M-index is demonstrated by several QSPR/QSAR models for different physico-chemical properties and biological activities of a large number of diversified compounds. Moreover, the applicability of the proposed index has been checked among isomeric compounds. In each case the stability of the obtained model is confirmed by the cross validation test. The results of present study indicate that the M-index provides a promising route for developing highly correlated QSPR/QSAR models. On the other hand, the M-index is easy to generate and the developed QSPR/QSAR models based on this index are linearly correlated. This is an interesting feature of the M-index when compared with quantum chemical descriptors which require vast computational cost and exhibit limitations for large sized molecules.