for which temperature dependent T product scaled per [Mn1.5Cr] unit was calculated as showed in Figure . Even this simplistic model nicely shows that with increasing antiferromagnetic exchange T product (in cm 3 Kmol -1 ) at room temperature starts to decline from value 8.3 for J = -1 cm -1 , through value 7.5 for J = -10 cm -1 to value 6.7 for J = -20 cm -1 (Figure ). This nicely explains much lower experimental value of T product of 1 at room temperature. Second feature of the experimental magnetic data, the increase of T product at lower temperatures, is also recovered successfully. We are aware that model in Eq.3 is very simple and does not cover properly all magnetic interactions in the 2D sheets of 1, thus more sophisticated spin Hamiltonian was proposed as qualitatively reproduce magnetic behaviour of 1. Thus, the magnetic data were computed for series of Jvalues as depicted in Figure . The temperature profile of T product is now more similar to experimental magnetic data, because there is larger increase of T at lower temperatures below 100 K. Thus, it is evident that the interplay of antiferromagnetic exchange interactions in 1D ladder-like system indeed leads to the large increase of T at lowest temperatures. open-source program EspinS. Here, the general Hamiltonian comprising the magnetic exchange within the program is defined as