Study of Substituent Effects on the Photoconductivity of Soluble 2,(3)- and 1,(4)-Substituted Phthalocyaninato- and Naphthalocyaninatotitanium(IV) Oxides

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• 作者：G&ouml ; tz Winter ; Heino Heckmann ; Peter Haisch ; Wolfgang Eberhardt ; Michael Hanack ; Larry L&uuml ; er ; Hans-Joachim Egelhaaf ; and Dieter Oelkrug
• 刊名：Journal of the American Chemical Society
• 出版年：1998
• 出版时间：November 18, 1998
• 年：1998
• 卷：120
• 期：45
• 页码：11663 - 11673
• 全文大小：312K
• 年卷期：v.120,no.45(November 18, 1998)
• ISSN：1520-5126

文摘

Soluble alkyl (II, 8a,b), fluoroalkyl (4a), and fluoroalkoxy (4b,c, 8c) 1,(4)- or 2,(3)-substitutedphthalocyaninato- and linear 2,(3)- and angular 1,(2)-annulated naphthalocyaninatotitanium(IV) oxides 10,12, and 14 were synthesized and characterized with regard to their spectroscopic, photophysical, andphotochemical properties. While alkyl- and fluoroalkoxy-substituted compounds are highly soluble in nonpolarsolvents, e.g., hexane, fluoroalkyl-substituted compounds are better soluble in polar aprotic solvents such asacetone. The stability against photooxidation in solution is enhanced on going from alkylated phthalocyanines1,(4)-(C₅H₁₁)₈PcTiO (8a), 1,(4)-(C₆H₁₃)₈PcTiO (8b), and 2,(3)-(C₄H₉)₈PcTiO (II) to fluorinated phthalocyanines2,(3)-(CF₃)₄PcTiO (4a), 2,(3)-(CF₃CH₂O)₄PcTiO (4b), and 2,(3)-(CF₃CH₂O)₈PcTiO (4c), from phthalocyaninesto naphthalocyanines (tert-butyl)₄-2,(3)-NcTiO (10), 1,(2)-NcTiO (12), and (tert-butyl)₄-1,(2)-NcTiO (14), andon going from 2,(3)-substituted 4a-c to 1,(4)-substituted phthalocyanines 8a-c. Thin films of these compounds,prepared by either vacuum deposition or spin casting, are classified into three types according to increasingintermolecular mages/gifchars/pi.gif" BORDER=0 >-mages/gifchars/pi.gif" BORDER=0 > interactions. Type mages/gifchars/alpha.gif" BORDER=0> films, characterized by absence of exciton splitting, are formedfrom 1,(4)-substituted phthalocyanines 8a-c. These films show low dark conductivities and photoconductivitiesand are considerably sensitive to photooxidation. Type mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> films, characterized by weak exciton splitting, areformed from fluorinated phthalocyanines 4a-c as well as from rapidly deposited 2,(3)-substituted phthalocyanines II and the unsubstituted PcTiO (I). These films show enhanced photoconductivity and are generallymore stable against photooxidation than type mages/gifchars/alpha.gif" BORDER=0> films. Type mages/gifchars/gamma.gif" BORDER=0 > films, formed by slow deposition of II, 10 andunsubstituted phthalocyanine I, are classified by a largely red-shifted B-band absorbing in the near-IR. Thesefilms are highly photosensitive as well as stabilized against photooxidation. Steady-state photoconductivitiesand dark conductivities in thin films are strongly dependent on oxygen partial pressure. Alkylated PcTiO'ssuch as 8a, 8b, and II are found to be p-type conductors (positive oxygen influence on conductivities) likeunsubstituted PcTiO (I), whereas angularly annulated naphthalocyanines such as 12 and 14 as well as fluorinatedPcTiO's 4a-c are n-type conductors (negative oxygen influence on conductivity). These findings arerationalized by comparison with experimental and theoretical literature data.