We investigate minimizers defined on a bounded domain Ω in R 2 for singular constrained energy functionals that include Ball and Majumdar's modification of the Landau-de Gennes Q-tensor model for nematic liquid crystals. We prove regularity of minimizers with finite energy and show that their range on compact subdomains of Ω does not intersect the boundary of the constraining set. We apply this result to prove that minimizers of the constrained Landau-de Gennes Q-tensor energy for liquid crystals composed of a singular Maier-Saupe bulk term and all elasticity terms with coefficients L 1 , • • • , L 5 , are C 2 in Ω; and their eigenvalues on compact subsets of Ω are contained in closed subintervals of the physical range (− 1 3 , 2 3 ).