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Certain physical properties associated with certain space groups or point groups · Piezoelectricity is the property of a crystal to develop an electric charge when subjected to pressure or tension in certain directions and is observed in crystals with polar axes.
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Certain physical properties associated with certain space groups or point groups ·Piezoelectricity is the property of a crystal to develop an electric charge when subjected to pressure or tension in certain directions and is observed in crystals with polar axes. oApplications of piezoelectricity include (but are not limited to) quartz timepieces and microphones; triboluminescence….later ·Optical activity refers to the ability of crystals to rotate plane-polarized light. ·Pyroelectricity is the property of a crystal to develop electrical polarization when the temperature is changed and can only occur in non-centrosymmetric crystal systems. ·Ferroelectricity (important in electro-ceramics) also shows polarization for a temperature change but has the additional feature of changing the direction of polarization in an electric field. See Table below for a listing of the point groups that exhibit the above-mentioned properties
Literature case studies TRIBOLUMINESCENCE: Non-centric space groups Conducting materials Segregated 1-D stacks Magnetic materials Integrated 1-D stacks Photoluminescent materials Packing by closed-shell metal-metal interactions
General Almost exclusively seen in crystalline samples Luminescent species the surrounding gas (N2) the compound itself a combination of both 11 eV ground state A Structural Study of Triboluminescence (TL) TL spectrum of sucrose Energy level of N2 emission excitation piezoelectricity Noncentrosymmetric space group
Zink’s “golden rule” : • only noncentrosymmetric crystals could be triboluminescent. • See ABSTRACT & TABLE 1 IN HANDOUT: • B. P. Chandra, J. I. Zink, Inorg. Chem., 1980, 19, 3098. • Some other papers by Professor Zink about triboluminescence: • Zink, J.; Hardy, G. E.; Sutton, J. E., J. Phys. Chem., 1976, 80, No.3, 248. • G. E. Hardy; J. I. Zink, Inorg. Chem., 1976, 15, 3061. • B. P. Chandra, J. I. Zink, J. Phys. Chem., 1982, 86, 4138
Zink’s Rule is Valid for 11 Tetrahedral Mn(II) Complexes Cotton, F. A.; Daniels, L. M.; Huang, P. Inorg. Chem.2001, 40, 3576.
SECOND HANDOUTRefutation of a Claimed Exception to Zink’s Rule: (TEA)[Eu(DBM)4] redetermine I2/a Z = 4 Ia Z = 4 R1 = 0.0581 wR2 = 0.0952 Flack x = 0.00(2) R(F) = 0.0749 R(wF) = 0.0817 Cotton, F. A.; Daniels, L. M.; Huang, P. Inorg. Chem. Comm., 2001, 4, 319. Sweeting, L. M.; Rheingold, A. L. J. Am. Chem. Soc., 1987, 109, 2652.
Three Genuine Exceptions to Zink’s Rule: Structural Redeterminations (piperidinium)[Eu(BA)4] [Tb(antipyrine)6]I3 [TbCl2(H2O)6]Cl P2/nZ = 2 R1 = 0.0147 wR2 = 0.0317 R Z = 3 P21/n Z = 4 R1 = 0.0253 WR2 = 0.0601 R1 = 0.0573 WR2 = 0.0887 Rheingold, A. L.; King, W., Inorg. Chem., 1989, 28, 1715.
Not Every Noncentrosymmetric Eu(III) Complexes Are Observably Triboluminescent Not Triboluminescent Eu2(phen)2(C8H7O2)6 ]•2H2O Na3[Eu(ODA)3]•8H2O Cc Z = 4 R1 = 0.0547 WR2 = 0.1214 Cc Z = 4 R1 = 0.0255 WR2 = 0.0699 Albin, M.; Whittle, R. R.; Horrocks, W. D. Inorg. Chem.1985, 24, 4591. Jin, L.-P.; Wang, R.-F. Chem. J. Chin. Univ.1993, 14, 1195.
