NOVELTY - Substituted heterocyclic compounds (I) are new.    USE - (I) are useful: in a hole transport material, an electro-optic or optoelectronic device, an optical LED, an organic photovoltaic device, an imaging member for forming an electrostatic latent image device, an organic thin film transistor, a dye sensitized solar cell device, an optical LED lighting panel, a printed device and a quantum dot based electroluminescent device, where the optical LED device used as a light source to print conductive, resistive, dielectric, piezoelectric or pyroelectric films or lines or grids, and the electro-optic or optoelectronic device is an optical LED and is part of a flat panel display, an imaging member for creation of an electrostatic latent image, an optical LED lighting panel, a photovoltaic device and a thin film transistor (all claimed); and as electron transporters in organic photovoltaics and semiconductors in thin film transistor devices.    ADVANTAGE - (I): are in pure form as a result of sublimation (claimed); have good hole transport properties and provide improved performance and lifetime when used in optical LEDs and other electro-optic or optoelectronic devices; and exhibit a favorable combination of hole mobility and high glass transition temperature or melting point.    DETAILED DESCRIPTION - Substituted heterocyclic compounds of formula (I) are new.    Ar1 = thianthrene moiety optionally mono-, bi- or poly- substituted by phenyl, biphenyl, naphthyl, anthryl, pyridyl, thienyl (all optionally further substituted by 1-4C alkyl-, 1-4C alkoxy- or F), 1-4C alkyl-, 1-4C alkoxy- or F;    Ar2 = chain aromatic ring system (optionally containing at least one O or S), polycyclic chain or fused aromatic ring system (optionally containing N or S), triarylamine moiety (linked to Ar1 via aryl, where the aryl rings are phenyl, naphthyl or anthracenyl), diarylamino moiety (where N of which is linked to Ar1), triarylphosphine oxide or arylsilane, where each ring of Ar2 is optionally substituted by 1-4C alkyl-, 1-4C alkoxy- or F, Ar1 and Ar2 are linked directly or through aryl or aryl vinyl, and the linkages at Ar1 are at 1,2-, 1,6-, 1,9-, 2,7- or 2,8- positions;    m = 1-4; and    n = 1 or 2.    INDEPENDENT CLAIMS are also included for:    (1) poly(diphenyl-(4-thianthren-1-yl-phenyl)-amine) of formula (IX);    (2) either 4-(thianthren-1-yl)triphenylphosphine oxide or 4-(thianthren-2-yl)triphenylphosphine oxide;    (3) 1,1'-(4,4'-oxybis(4,1-phenylene))dithianthrene;    (4) 4,4'-bis(3-(10H-phenothiazin-10-yl)styryl)biphenyl;    (5) a hole transport material comprising a compound (Q2) comprising (I), (IX), either 4-(thianthren-1-yl)triphenylphosphine oxide or 4-(thianthren-2-yl)triphenylphosphine oxide, 1,1'-(4,4'-oxybis(4,1-phenylene))dithianthrene or 4,4'-bis(3-(10H-phenothiazin-10-yl)styryl)biphenyl, and a para-dopant which is an acceptor-type organic molecule;    (6) an optical LED having first and second electrodes and a layer comprising the compound (Q2) or the hole transport material, between the electrodes;    (7) an organic photovoltaic device including the compound (Q2) or the hole transport material;    (8) an imaging member for forming an electrostatic latent image device including the compound (Q2) or the hole transport material;    (9) an organic thin film transistor comprising the compound (Q2) or the hole transport material;    (10) a dye sensitized solar cell device comprising the compound (Q2) or the hole transport material;    (11) a printed device comprising the compound (Q2) or the hole transport material;    (12) a quantum dot based electroluminescent device comprising the compound (Q2) or the hole transport material;    (13) an electro-optic or optoelectronic device having a compound (Q1) having one or two thianthrene moieties linked to conjugated or aromatic hydrocarbon other than alkyl substituted fluorene;    (14) an optical LED device having a first electrode, a layer comprising 1-anthracenyl-9-yl-thianthrene, 1-biphenyl-4-yl-thianthrene or 9,10-bis(1-thianthrenyl)anthracene and a second electrode and optionally a low work function material;    (15) sublimation purified 4,4'-di-(thianthren-1-yl)triphenylamine;    (16) sublimation purified 2,8-bis(1-thianthrenyl)dibenzothiophene; and    (17) sublimation purified 9,10-bis(1-thianthrenyl)anthracene.    b = not defined.