\textbf{Vanadyl Phthalocyanine (C}$_{\mathrm{\mathbf{32}}}$\textbf{H}$_{\mathrm{\mathbf{16}}}$\textbf{N}$_{\mathrm{\mathbf{8}}}$\textbf{VO): a near-perfect molecular paramagnet}

Transition-metal-doped phthalocyanines (TMPc, TM $=$ Mn, Fe, Co, Ni, and Cu) are semiconductors with interesting photoconductive properties and so have potential applications in optoelectronic devices [1]. TMPc are planar molecules with the TM atom at the center bound to four N atoms and forming a linear chain along the monoclinic b-axis. Recent magnetic studies reported in CuPc, CoPc, and MnPc show that the exchange coupling between the TM ions are either ferromagnetic as in MnPc [2] or antiferromagnetic as in CuPc [3] and CoPc [4]. In contrast to TMPc, VOPc has a five- coordinate square pyramidal structure with a single electron associated with VO$^{\mathrm{2+}}$ ion [5]. Here we report results from detailed investigations of the magnetic properties of powder sample of VOPc X-ray diffraction of which shows it to be triclinic. Temperature dependence of magnetization M from 2 K to 300 K in H $=$ 1 kOe fits the Curie-Weiss (CW) law with $\theta \quad =$ 0 K, $\mu \quad =$ 1.665$\mu_{\mathrm{B}}$ and g $=$ 1.922 for spin S $=$ 1/2 which indicates VOPc is paramagnetic without any exchange coupling between VO$^{\mathrm{2+}}$ ions, quite different from CuPc, CoPc and MnPc. Also, M vs. H data (up to 90 kOe) at 2 K, 5 K, 10 K, 25 K, 50 K, 100 K, and 300 K fit well with the Brillouin function variation for S $=$ \textonehalf , again confirming perfect paramagnetism in VOPc. [1]S.Heutz et al. Adv. Mater.19, 3618 (2007). [2]J.E.Brumboiu et al, J. Phys. Chem. A. 118, 927(2014). [3]Z.Wang et al, IEEE Trans. Magn. 51, 2700104(2015). [4]M.Serri et al, Nature Commun. 5, 3079(2014). [5]H.Adler et al, J. Phys. Chem. C. 119, 8755 (2015).