Compounds of formula (I) or a pharmaceutically acceptable salt, solvate or prodrug thereof, are disclosed: wherein R1 is C1-6alkyl, haloC1-6alkyl, C2-6alkenyl, amino, monoC1-4alkylamino or diC1-4alkylamino; R2 and R3, which may be the same or different, are hydrogen, halogen, C1-6alkyl, haloC1-6alkyl, C1-4alkoxy, haloC1-4alkoxy, cyano, amino, monoC1-4alkylamino or diC1-4alkylamino; each R4, which may be the same or different, is C1-6alkyl, halogen, C1-6alkyl, haloC1-6alkyl, C1-4alkoxy, haloC1-4alkoxy, cyano, nitro, amino, monoC1-4alkylamino or diC1-4alkylamino; p is 0, 1 or 2; n is 1 or 2; R5 and R6, which may be the same or different, are hydrogen, halogen, C1-6alkyl, haloC1-6alkyl, C1-4alkoxy, haloC1-4alkoxy, cyano, amino, monoC1-4alkylamino or diC1-4alkylamino; and Het is thienyl, pyridyl, pyrimidinyl, pyridazinyl, pyrimidinyl, pyrazinyl, imidazolyl, pyrazolyl, pyrrolyl, quinolyl, thiazolyl or furyl, each of which may be substituted by one or more groups independently selected from the list consisting of C1-6alkyl, C1-6alkoxy, acetyl, halogen, haloC1-6alkyl, cyano, nitro, amino, monoC1-4alkylamino and diC1-4alkylamino. Methods of preparation of the compounds, and uses thereof in medicine, for example treatment of schizophrenia, are also disclosed.