, At the end of our trip, we saw that both Ir(I) and Ir(III) complexes can present large TPA cross-sections and thus large TPA cross-section materials are accessible with tunable emission properties for applications in photonics and biomedicine

, We thank MIUR and the National Interuniversity Consortium of Materials Science and Technology

N. P. Prasad and D. J. Williams, Introduction to Nonlinear Optical Effects in molecules and Polymers, 1991.

J. Zyss, Molecular Nonlinear Optics: Materials, Physics and Devices, 1994.

, Optoelectronic Properties of Inorganic Compounds

D. M. Roundhill, J. P. Fackler, and . Ed, , 1999.

M. L. Green, S. R. Marder, M. E. Thompson, J. A. Bandy, D. Bloor et al., Synthesis and structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl) ethylene], an organotransition metal compound with a large second-order optical nonlinearity, Nature, vol.330, pp.360-362, 1987.

H. S. Nalwa, Organometallic materials for nonlinear optics, Appl. Organomet. Chem, vol.5, pp.349-377, 1991.

S. R. Marder, Inorganic Materials, pp.115-164, 1992.

N. J. Long, Organometallic Compounds for Nonlinear Optics-The Search for En-light-enment!, Angew. Chem. Int. Ed. Engl, vol.34, pp.21-38, 1995.

I. R. Whittall, A. M. Mcdonagh, M. G. Humphrey, and S. Samoc, Organometallic Complexes in Nonlinear Optics I: Second-Order Nonlinearities, Adv. Organomet Chem, vol.42, pp.291-362, 1998.

J. Heck, S. Dabek, T. Meyer-friedrichsen, and H. Wong, Mono-and dinuclear sesquifulvalene complexes, organometallic materials with large nonlinear optical properties, Coord. Chem. Rev, pp.1217-1254, 1999.

H. L. Bozec and T. Renouard, Dipolar and Non-Dipolar Pyridine and Bipyridine Metal Complexes for Nonlinear Optics, Eur. J. Inorg. Chem, pp.229-239, 2000.

C. E. Powel and M. G. Humphrey, Nonlinear otical properties of transition metal acetylides and their derivatives, Coord. Chem. Rev, vol.248, pp.725-756, 2004.

S. and D. Bella, Second-order nonlinear optical properties of transition metal complexes, Chem. Soc. Rev, vol.30, pp.5-366, 2001.

B. J. Coe, Comprehensive Coordination Chemistry II

, Nonlinear Optical Properties of Metal Complexes, vol.9, pp.621-687, 2004.

B. J. Coe and N. R. Curati, Metal complexes for molecular electronics and photonics, Comments on Inorg. Chem, vol.25, pp.147-184, 2004.

O. Maury and H. L. Bozec, Molecular Engineering of Octupolar NLO Molecules and Materials Based on Bipyridyl Metal Complexes, Acc. Chem. Res, vol.38, pp.691-704, 2005.

E. Cariati, M. Pizzotti, D. Roberto, F. Tessore, and R. Ugo, Coordination and organometallic compounds and inorganic-organic hybrid crystalline materials for second-order non-linear optics, Coord Chem Rev, vol.250, pp.1210-1233, 2006.

B. J. Coe, Switchable nonlinear optical metallochromophores with pyridinium electron acceptor groups, Acc. Chem. Res, vol.39, pp.383-393, 2006.

B. J. , Coe in Non-Linear Optical Properties of Matter (G. Papadopoulos, Manthos, Sadlej, Ruthenium Complexes as Versatile Chromophores with Large, Switchable Hyperpolarizabilities, pp.571-608, 2006.

J. P. Morrall, G. T. Dalton, M. G. Humphrey, and M. Samoc, Organotransition metal complexes for nonlinear optics, Adv. Organomet. Chem, vol.55, pp.61-136, 2007.

S. D. Bella, C. Dragonetti, M. Pizzotti, D. Roberto, F. Tessore et al., Topics in Organometallic Chemistry 28. Molecular Organometallic Materials for Optics, vol.28, p.1, 2010.

O. Maury, H. L. Bozec, ;. D. Bruce, D. O'hare, R. I. Walton et al., Metal-based quadratic molecular materials, Molecular Materials, p.1, 2010.

M. G. Humphrey, T. Schwich, P. J. West, M. P. Cifuentes, and M. Samoc, Comprehensive Inorganic Chemistry II, vol.8, 2013.

M. Pizzotti, R. Ugo, D. Roberto, S. Bruni, P. Fantucci et al., Organometallic Counterparts of Push-Pull Aromatic Chromophores for Nonlinear Optics: Push-Pull Heteronuclear Bimetallic Complexes with Pyrazine and trans-1,2-bis(4-pyridyl)ethylene as Linkers, Organometallics, vol.21, pp.5830-5840, 2002.

J. L. Oudar and D. S. Chemla, Hyperpolarizabilities of the nitroanilines and their relations to the excited state dipole moment, J. Chem. Phys, vol.66, pp.2664-2668, 1977.

J. L. Oudar, Optical nonlinearities of conjugated molecules. Stilbene derivatives and highly polar aromatic compounds, J. Chem. Phys, vol.67, pp.446-457, 1977.

D. R. Kanis, M. A. Ratner, and T. J. Marks, Optical nonlinearities of conjugated molecules. Stilbene derivatives and highly polar aromatic compounds, Chem. Rev, vol.67, pp.195-242, 1994.

L. T. Cheng, W. Tam, S. H. Stevenson, G. R. Meredith, G. Rikken et al., Experimental investigations of organic molecular nonlinear optical polarizabilities. 1. Methods and results on benzene and stilbene derivatives, J Phys Chem, vol.95, pp.10631-10643, 1991.

L. T. Cheng, W. Tam, S. R. Marder, A. E. Stiegman, G. Rikken et al., Stronger acceptors can diminish nonlinear optical response in simple donor-acceptor polyenes, J. Phys. Chem, vol.95, pp.10643-10652, 1991.

L. Beverina, R. Ruffo, G. Patriarca, F. De-angelis, D. Roberto et al., Second harmonic generation in nonsymmetrical squaraines: tuning of the directional charge transfer character in highly delocalized dyes, J. Mater. Chem, vol.19, pp.8190-8197, 2009.

L. R. Dalton, P. A. Sullivan, and D. H. Bale, Electric Field Poled Organic Electro-optic Materials: State of the Art and Future Prospects, Chem. Rev, vol.110, pp.25-55, 2010.

K. D. Singer, E. Sohn, L. A. King, K. M. Gordon, H. E. Katz et al., Second-order nonlinear-optical properties of donor-and acceptor-substituted aromatic compounds, J. Opt. Soc. Am. B, vol.6, p.1339, 1989.

M. A. Marques, M. , E. K. Gross, and E. , Time-dependent density functional theory, Annual Rev. Phys. Chem, vol.55, pp.427-455, 2004.
URL : https://hal.archives-ouvertes.fr/hal-00438357

I. Ledoux and J. Zyss, Influence of the molecular environment in solution measurements of the second-order optical susceptibility for urea and derivatives, Chem. Phys, vol.73, pp.203-213, 1982.

E. A. Guggenheim, A proposed simplification in the procedure for computing electric dipole moments, Trans. Faraday Soc, vol.45, pp.714-720, 1949.

P. D. Maker, Spectral broadening of elastic second-harmonic light scattering in liquids, Phys. Rev. A, vol.1, pp.923-951, 1970.

K. Clays, K. Persoons, and A. , Hyper-Rayleigh scattering in solution, Phys. Rev. Lett, vol.66, pp.2980-2983, 1991.

J. Zyss, Molecular engineering implications of rotational invariance in quadratic nonlinear optics: From dipolar to octupolar molecules and materials, J. Chem. Phys, vol.98, pp.6583-6600, 1993.

J. Zyss and I. Ledoux, Nonlinear optics in multipolar media: theory and experiments, Chem. Rev, vol.94, pp.77-105, 1994.

B. J. Coe, Developing iron and ruthenium complexes for potential nonlinear optical applications, Coord. Chem. Rev, vol.257, pp.1438-1458, 2013.

S. D. Bella, A. Colombo, C. Dragonetti, S. Righetto, and D. Roberto, Zinc(II) as a versatile template for the preparation of fascinating dipolar and octupolar second-order nonlinear optical molecular materials, Inorganics, vol.6, p.133, 2018.

C. Dragonetti, A. Colombo, D. Marinotto, S. Righetto, D. Roberto et al., Functionalized styryl Iridium(III) complexes as active second-order NLO chromophores and building blocks for SHG polymeric films, J. Organomet. Chem, vol.751, pp.568-572, 2014.
URL : https://hal.archives-ouvertes.fr/hal-00915105

E. Zysman-colman, Iridium(III) in Optoelectronic and Photonics Applications, 2017.

D. W. Bruce and A. Thornton, Electronic Hyperpolarisabilities of Some Mesogenic Stilbazole Complexes of Rh (I) and Ir (I), Mol. Cryst. Liq. Cryst, vol.231, pp.253-256, 1993.

D. Roberto, R. Ugo, S. Bruni, E. Cariati, F. Cariati et al.,

J. Ledoux and . Zyss, Quadratic Hyperpolarizability Enhancement of para-Substituted Pyridines Upon Coordination to Organometallic Moieties: the Ambivalent Donor or Acceptor Role of the Metal, Organometallics, vol.19, pp.1775-1788, 2000.

D. Locatelli, S. Quici, D. Roberto, and F. De-angelis, The Unexpected Similar Second Order NLO Response for Nearly Planar and Largely Twisted Push-Pull Stilbazole Chromophores: an EFISH and Theoretical TD-DFT Evidence, Chem. Commun, pp.5405-5407, 2005.

V. Calabrese, S. Quici, E. Rossi, E. Cariati, C. Dragonetti et al., Highly stable 7-N,N-dibutylamino-2-azaphenanthrene and 8-N,Ndibutylamino-2-azachrysene as a new class of second order NLO-active chromophores, Chem. Commun, vol.4, pp.8374-8376, 2010.

L. Cheng, W. Tam, and D. F. Eaton, Quadratic hyperpolarizabilities of Group 6A metal carbonyl complexes, Organometallics, vol.9, pp.2856-2857, 1990.

D. R. Kanis, P. G. Lacroix, M. A. Ratner, and T. J. Marks, Electronic Structure and Quadratic Hyperpolarizabilities in Organotransition Metal Chromophores Having Weakly Coupled ?

. Networks, Unusual Mechanisms for Second-Order Response, J. Am. Chem. Soc, vol.116, pp.10089-10102, 1994.

M. Pizzotti, R. Ugo, C. Dragonetti, E. Annoni, F. Demartin et al., Unexpected Formation of a Week Metal-Metal Bond: Synthesis, Electronic Properties and Second-Order NLO Responses of Push-Pull Late-Early Heteronuclear Bimetallic Complexes with, Organometallics, vol.22, pp.4001-4011, 2003.

D. Roberto, F. Tessore, R. Ugo, S. Bruni, A. Manfredi et al., Ru(III) and Ir(III) complexes as new asymmetric chromophores for nonlinear optics: first evidence for a shift from positive to negative value of the quadratic hyperpolarizability of a ligand carrying an electron donor substituent upon coordination to different metal centres, Terpyridine Zn(II), pp.846-847, 2002.

F. Tessore, D. Roberto, R. Ugo, M. Pizzotti, M. Quici et al., Ru(III), and Ir(III) Complexes: The Relevant Role of the Nature of the Metal Ion and of the Ancillary Ligands on the Second-Order Nonlinear Response of Terpyridines Carrying Electron Donor or Electron Acceptor Groups, Terpyridine Zn(II), vol.44, pp.8967-8978, 2005.

D. Locatelli, S. Quici, S. Righetto, D. Roberto, F. Tessore et al., Secondharmonic generation from monolayer Langmuir-Blodgett films of various push-pull pyridine and terpyridine metal complexes, Progress in Solid State Chemistry, vol.33, pp.223-232, 2005.

M. Bourgault, K. Baum, H. L. Bozec, G. Pucetti, I. Ledoux et al., Synthesis and molecular hyperpolarisabilities of donor-acceptor bipyridyl metal complexes (M= Re, Zn, Hg), New J. of Chem, pp.517-522, 1998.

F. Tessore, D. Roberto, R. Ugo, P. Mussini, S. Quici et al., Concentration-Dependent Enhancement of the Quadratic Hyperpolarizability of [Zn(CH 3 CO 2 ) 2 (L) 2 ] in CHCl 3 on Substitution of Acetate by Triflate, Angew. Chem. Int. Ed, vol.42, pp.456-459, 2003.

V. Aubert, V. Guerchais, E. Ishow, K. Hoang-thy, I. Ledoux et al., Efficient Photoswitching of the Nonlinear Optical Properties of Dipolar Photochromic Zinc(II) Complexes, Angew. Chem. Int. Ed, vol.47, pp.577-580, 2008.
URL : https://hal.archives-ouvertes.fr/hal-00369113

A. Colombo, C. Dragonetti, S. Righetto, D. Roberto, A. Valore et al., Novel highly conjugated push-pull 4,5-diazafluoren-9-ylidene based efficient NLO chromophores as a springboard for coordination complexes with large second-order NLO properties, J. Mater. Chem, vol.22, pp.19761-19766, 2012.

A. Valore, A. Colombo, C. Dragonetti, S. Righetto, D. Roberto et al., Luminescent cyclometalated Ir(III) and Pt(II) complexes with ?-diketonate ligands as highly active second-order NLO chromophores, Chem. Commun, vol.46, pp.2414-2416, 2010.

R. Macchi, E. Cariati, D. Marinotto, D. Roberto, E. Tordin et al., Stable SHG from in situ grown oriented nanocrystals of [(E)-N,Ndimethylamino-N?-methylstilbazolium, PMMA film J. Mater. Chem, vol.20, pp.1885-1890, 2010.

M. Zaarour, V. Guerchais, H. L. Bozec, C. Dragonetti, S. Righetto et al., An investigation on the second order nonlinear optical of tris-cyclometallated Ir(III) complexes with variously substituted 2-phenylpyridines, Dalton. Trans, vol.42, pp.155-159, 2013.
URL : https://hal.archives-ouvertes.fr/hal-00879510

M. Zaarour, A. Singh, C. Latouche, J. A. Williams, I. Ledoux-rak et al., Linear and Nonlinear Optical Properties of Tris-cyclometalated Phenylpyridine Ir(III) Complexes Incorporating ?-Conjugated Substituents, Inorg. Chem, vol.52, pp.7987-7994, 2013.
URL : https://hal.archives-ouvertes.fr/hal-00874141

J. Breu, P. Stössel, S. Schrader, . Starukhin, W. J. Finkenzeller et al., Crystal structure of fac-Ir(ppy) 3 and emission properties under ambient conditions and at high pressure, Chem. Mater, vol.17, pp.1745-1752, 2005.

T. L. Bouder, L. Viau, J. Guégan, O. Maury, and H. L. Bozec, Hydroxy-Functionalized Bipyridine and Tris(bipyridine) metal Chromophores: Synthesis and Optical Properties, Eur. J. Org. Chem, pp.3024-3033, 2002.

C. G. Claessens, D. Gonzalez-rodriguez, T. G. Torres, F. Martin, and . Agullo-lopez,

I. Ledoux, J. Zyss, V. R. Ferro, J. Garcia-de-la, and . Vega, Structural Modulation of the Dipolar? Octupolar Contributions to the NLO Response in Subphthalocyanines, J. Phys. Chem. B, vol.109, pp.3800-3809, 2005.

M. S. Lowry and S. Bernhard, Synthetically tailored excited states: phosphorescent, cyclometalated iridium (III) complexes and their applications, Chem. Eur. J, vol.12, pp.7970-7977, 2006.

F. De-angelis, S. Fantacci, N. Evans, C. Klein, S. M. Zakeeruddin et al., Controlling phosphorescence color and quantum yields in cationic iridium complexes: a combined experimental and theoretical study, Inorg. Chem, vol.46, pp.5989-6001, 2007.

Q. Zhao, S. Liu, M. Shi, C. Wang, M. Yu et al., Series of New Cationic Iridium(III) Complexes with Tunable Emission Wavelength and Excited State Properties: Structures, Theoretical Calculations, and Photophysical and Electrochemical Properties, vol.45, pp.6152-6160, 2006.

H. J. Bolink, E. Cappelli, E. Coronado, M. Graetzel, E. Orti et al.,

. Nazeeruddin, Stable single-layer light-emitting electrochemical cell using 4, 7-diphenyl-1, 10-phenanthroline-bis (2-phenylpyridine) iridium (III) hexafluorophosphate, J. Am. Chem. Soc, vol.128, pp.14786-14787, 2006.

C. Dragonetti, L. Falciola, P. Mussini, S. Righetto, D. Roberto et al., The Role of Substituents on Functionalized 1,10-Phenanthroline in Controlling the Emission Properties of Cationic Iridium(III) Complexes of Interest for Electroluminescent Devices, Inorg. Chem, vol.46, pp.8533-8547, 2007.

C. Dragonetti, S. Righetto, D. Roberto, R. Ugo, A. Valore et al., Cyclometallated Iridium(III) complexes with substituted 1,10-phenanthrolines: a new class of highly active organometallic second order NLO-phores with excellent transparency with respect to second harmonic emission, Chem. Commun, vol.40, pp.4116-4118, 2007.

V. Alain, M. Blanchard-desce, I. Ledoux-rak, and J. Zyss, Amphiphilic polyenic push-pull chromophores for nonlinear optical applications, Chem. Commun, pp.353-354, 2000.

C. Dragonetti, S. Righetto, D. Roberto, A. Valore, T. Benincori et al., Cationic cyclometallated iridium(III) complexes with substituted 1,10-phenanthrolines: the role of the cyclometallated moiety on this new class of complexes with interesting luminescent and second order non linear optical properties, J Mater Sci: Mater. Electron, vol.20, pp.460-464, 2009.

C. Dragonetti, S. Righetto, D. Roberto, and A. Valore, The role of the cyclometalated moiety on the second order nonlinear optical properties of cationic Ir(III) organometallic NLOphores, Phys. Status Solid C, vol.6, pp.50-53, 2009.

C. Dragonetti, S. Righetto, D. Roberto, R. Ugo, A. Valore et al., The role of 5-R-1,10-phenanthroline (R = CH 3 , NO 2 ) on the emission properties and second order NLO response of cationic Ir(III) organometallic chromophores, Inorg. Chim. Acta, vol.61, pp.4070-4076, 2008.

A. Valore, E. Cariati, C. Dragonetti, S. Righetto, D. Roberto et al., Cyclometalated Ir III Complexes with Substituted 1,10-Phenanthrolines: A New Class of Efficient Cationic Organometallic Second-Order NLO Chromophores, Chem. Eur. J, vol.16, pp.4814-4825, 2010.

A. Valore, M. Balordi, A. Colombo, C. Dragonetti, S. Righetto et al., Novel ruthenium(II) complexes with substituted 1,10-phenanthroline or 4,5-diazafluorene linked to a fullerene as highly active second order NLO chromophores, Dalton. Trans, vol.39, pp.10314-10318, 2010.

C. Dragonetti, A. Valore, A. Colombo, S. Righetto, G. Rampinini et al., An investigation on the second-order NLO properties of novel cationic cyclometallated Ir(III) complexes of the type, + (R = H, fulleridene) and the related neutral complex with the new 9-fulleriden-4-monoazafluorene ligand, vol.2, pp.72-78, 2012.

V. Aubert, L. Ordronneau, M. Escadeillas, J. A. Williams, A. Boucekkine et al.,

S. Dragonetti, D. Righetto, R. Roberto, A. Ugo, A. Valore et al.,

L. Bozec and V. Guerchais, Linear and nonlinear optical properties of cationic bipyridyl iridium(III) complexes: tunable and photoswitchable?, Inorg. Chem, vol.50, pp.5027-5038, 2011.
URL : https://hal.archives-ouvertes.fr/hal-00860254

M. Irie, Diarylethenes for memories and switches, Chem. Rev, vol.100, pp.1685-1716, 2000.

H. L. Bozec and V. Guerchais, Photochromic bipyridyl metal complexes: Photoregulation of the nonlinear optical and/or luminescent properties, Comptes Rendus Chimie, vol.16, pp.1172-1182, 2013.
URL : https://hal.archives-ouvertes.fr/hal-00947160

V. Guerchais, L. Ordronneau, and H. L. Bozec, Recent developments in the field of metalcomplexes containing photochromic ligands: Modulation of linear and nonlinear optical properties, Coord. Chem. Rev, vol.254, pp.2533-2545, 2010.

D. Marinotto, R. Castagna, S. Righetto, C. Dragonetti, A. Colombo et al., Photoswitching of the Second Harmonic Generation from Poled Phenyl-Substituted Dithienylethenes Thin Film and EFISH Measurements, J. Phys. Chem. C, vol.115, pp.20425-20432, 2011.

J. Boixel, V. Guerchais, H. L. Bozec, D. Jacquemin, A. Amar et al., Second-order NLO switches from molecules to polymer films based on photochromic cyclometalated platinum(II) complexes, J. Am. Chem. Soc, vol.136, pp.5367-5375, 2014.
URL : https://hal.archives-ouvertes.fr/hal-00992877

J. Boixel, V. Guerchais, H. L. Bozec, A. Chantzis, D. Jacquemin et al., Sequential double second-order nonlinear optical switch by an acido-triggered photochromic cyclometallated platinum(II) complex, Chem. Comm, vol.71, p.7805, 2015.
URL : https://hal.archives-ouvertes.fr/hal-01141732

V. Aubert, V. Guerchais, E. Ishow, K. Hoang-thi, I. Ledoux et al., Efficient photoswitching of the nonlinear optical properties of dipolar photochromic zinc (II) complexes, Angew. Chem. Int. Ed, vol.47, pp.577-580, 2008.
URL : https://hal.archives-ouvertes.fr/hal-00369113

V. Aubert, E. Ishow, V. Guerchais, H. L. Bozec, F. Ibersiene et al., A "reverse interrupter": the novel molecular design of a fluorescent photochromic DTE-based bipyridine, New. J. Chem, vol.33, pp.1320-1323, 2009.
URL : https://hal.archives-ouvertes.fr/hal-00442461

A. Colombo, E. Garoni, C. Dragonetti, S. Righetto, D. Roberto et al., A novel multifunctional cyclometallated iridium(III) complex with interesting second-order nonlinear optical properties and two-photon absorption activity, Polyhedron, vol.140, pp.116-121, 2018.
URL : https://hal.archives-ouvertes.fr/hal-01695552

C. Hierlinger, D. B. Cordes, A. M. Slawin, A. Colombo, C. Dragonetti et al., An investigation on the secondorder nonlinear optical response of cationic bipyridine or phenanthroline iridium(III) complexes bearing cyclometallated 2-phenylpyridines with a triphenylamine substituent, Dalton Trans. 47, pp.8292-8300, 2018.
URL : https://hal.archives-ouvertes.fr/hal-01834005

F. Tessore, E. Cariati, F. Cariati, D. Roberto, R. Ugo et al., The role of ion pairs in the second order NLO response of 4-X-1-Methylpyridinium salts, ChemPhysChem, vol.11, pp.495-507, 2010.

H. Wang, L. Jing, H. Wang, J. Ye, and Y. Qiu, Improving the NLO response of bis-cyclometalated iridium(?) complexes by modifying ligands: A DFT study, J. Organomet. Chem, vol.869, pp.18-25, 2018.

Y. Wang, D. Astruc, and A. S. Abd-el-aziz, Metallopolymers for advanced sustainable applications, vol.48, pp.558-636, 2019.

B. J. Coe, Molecular Materials Possessing Switchable Quadratic Nonlinear Optical Properties, Chem. Eur. J, vol.5, pp.2464-2471, 1999.

J. A. Delaire and K. Nakatani, Linear and Nonlinear Optical Properties of Photochromic Molecules and Materials, Chem. Rev, vol.100, pp.1817-1846, 2000.

I. Asselberghs, K. Clays, A. Persoons, M. D. Ward, and J. Mccleverty, Switching of molecular second-order polarisability in solution, J. Mater. Chem, vol.14, pp.2831-2839, 2004.

K. A. Green, M. P. Cifuentes, M. Samoc, and M. G. Humphrey, Metal alkynyl complexes as switchable NLO systems, Coord. Chem. Rev, vol.255, pp.2530-2541, 2011.

F. Castet, V. Rodriguez, J. Pozzo, L. Ducasse, A. Plaquet et al., Design and Characterization of Molecular Nonlinear Optical Switches, Acc. Chem. Res, vol.46, p.2656, 2013.

E. Cariati, C. Dragonetti, E. Lucenti, F. Nisic, S. Righetto et al., An acidotriggered reversible luminescent and nonlinear optical switch based on a substituted styrylpyridine: EFISH measurements as an unusual method to reveal a protonationdeprotonation NLO contrast, Chem. Commun, vol.50, pp.1608-1610, 2014.

F. Nisic, A. Colombo, C. Dragonetti, M. Fontani, D. Marinotto et al., Highly efficient acido-triggered reversible luminescent and nonlinear optical switch based on 5-?-delocalized-donor-1,3-di(2-pyridyl)benzenes, J. Mater. Chem. C, vol.3, pp.7421-7427, 2015.

V. Guerchais, J. Boixel, and H. L. Bozec, Linear and Nonlinear Optical Molecular Switches Based on Photochromic Metal Complexes, Photon-Working Switches, pp.363-384, 2017.

B. J. Coe, A. Avramopoulos, M. G. Papadopoulos, K. Pierloot, S. Vancoillie et al., Theoretical Modelling of Photoswitching of Hyperpolarisabilities in Ruthenium Complexes, vol.19, pp.15955-15963, 2013.

S. D. Bella, I. P. Oliveri, I. P. Colombo, C. Dragonetti, S. Righetto et al., An unprecedented switching of the second-order nonlinear optical response in aggregate bis(salicylaldiminato)zinc(II) Schiff-base complexes, pp.7013-7016, 2012.

S. Attar, D. Espa, F. Artizzu, L. Pilia, A. Serpe et al., Optically Multiresponsive Heteroleptic Platinum Dithiolene Complex with Proton-Switchable Properties, vol.56, pp.6763-6767, 2017.

D. Espa, L. Pilia, L. Marchiò, M. L. Mercuri, A. Serpe et al., Redox-Switchable Chromophores Based on Metal (Ni, Pd, Pt) Mixed-Ligand Dithiolene Complexes Showing Molecular Second-Order Nonlinear-Optical Activity, vol.50, pp.2058-2060, 2011.

H. Zhao, E. Garoni, T. Roisnel, A. Colombo, C. Dragonetti et al., Photochromic DTE-Substituted-1,3-di(2-pyridyl)benzene Platinum(II) Complexes: Photomodulation of Luminescence and Second-Order Nonlinear Optical Properties, Inorg. Chem, vol.57, pp.7051-7063, 2018.
URL : https://hal.archives-ouvertes.fr/hal-01817480

J. Wang, W. Wang, X. Fang, and Y. Qiu, Carborane tuning on iridium complexes: redox-switchable second-order NLO responses, J. Mol. Model, vol.21, 2015.

X. Li, H. Wang, J. Ye, Y. Zhang, and Y. Qiu, Second-order NLO properties of bis-cyclometalated iridium(?) complexes: Substituent effect and redox switch, J. Molec. Graph. Model, vol.89, pp.131-138, 2019.

Y. Shen, X. Li, J. Ye, and Y. Qiu, A DFT study on second-order NLO properties of bis-cyclometalated Iridium (III) complexes with chelating dicarbene auxiliary ligands, Computational and Theoretical Chem, vol.1163, p.112535, 2019.

E. Baggaley, J. A. Weinstein, and J. A. Williams, Lighting the way to see inside the live cell with luminescent transition metal complexes, Coord. Chem. Rev, vol.256, pp.1762-1785, 2012.

E. Baggaley, J. A. Weinstein, and J. A. Williams, Time-resolved emission imaging microscopy using phosphorescent metal complexes: Taking FLIM and PLIM to new lengths, Struct. Bond, vol.165, pp.205-256, 2015.

L. Murphy, A. Congreve, L. Palsson, and J. A. Williams, The time domain in co-stained cell imaging: time-resolved emission imaging microscopy using a protonatable luminescent iridium complex, Chem Commun, vol.46, pp.8743-8745, 2010.

P. Steunenberg, A. Ruggi, N. S. Van-den, T. Berg, T. ;. Buckle et al., -phenylpyridine)iridium(III) Complexes, Phosphorescence Imaging of Living Cells with Amino Acid-Functionalized Tris, vol.51, pp.2105-2114, 2012.

A. Colombo, M. Fontani, C. Dragonetti, D. Roberto, J. A. Williams et al.,

, Ir(III) complex with remarkable photoactivated anticancer activity, Chem. Eur. J, vol.25, pp.7948-7952, 2019.

W. R. Zipfel, R. M. Williams, and R. M. Webb, Nonlinear magic: multiphoton microscopy in the biosciences. Nonlinear magic: multiphoton microscopy in the biosciences, Nat. Biotechnol, vol.21, pp.1368-1376, 2003.

W. Denk, J. H. Strickler, and W. W. Webb, Two-photon laser scanning fluorescence microscopy. Two-photon laser scanning fluorescence microscopy, Science, vol.248, pp.73-76, 1990.

M. Pawlicki, H. A. Collins, R. G. Denning, and H. L. Anderson, Two-photon absorption and the design of two-photon dyes, Angew. Chem. Int. Ed, vol.48, pp.3244-3266, 2009.

R. L. Sutherland, Handbook of nonlinear optics, 2 nd edn, 2003.

S. Mazzucato, I. Fortunati, S. Scolaro, M. Zerbetto, C. Ferrante et al.,

. Ghezzi, Two-photon absorption of Zn (II) octupolar molecules, Phys. Chem. Chem. Phys, vol.9, pp.2999-3005, 2007.

M. Sheik-bahae, A. A. Said, T. Wei, D. G. Hagan, and E. W. Van-stryland, Sensitive measurement of optical nonlinearities using a single beam, IEEE J. Quant. Electr, vol.26, pp.760-769, 1990.

K. Kamada, K. Matsunaga, A. Yoshino, and K. Ohta, Two-photon-absorption-induced accumulated thermal effect on femtosecond Z-scan experiments studied with time-resolved thermal-lens spectrometry and its simulation, J. Opt. Soc. Am. B, vol.20, pp.529-537, 2003.

A. Colombo, C. Dragonetti, D. Roberto, A. Valore, C. Ferrante et al., Two-photon absorption properties and 1 O 2 generation ability of Ir complexes: unexpected large cross section of

, Dalton Trans, vol.44, pp.15712-15720, 2015.

F. Todescato, I. Fortunati, S. Carlotto, C. Ferrante, L. Grisanti et al., Dimers of polar chromophores in solution: role of excitonic interactions in one-and two-photon absorption properties, Phys. Chem. Chem. Phys, vol.13, pp.11099-11109, 2011.

C. Dragonetti, M. Balordi, A. Colombo, D. Roberto, R. Ugo et al., Two-photon absorption properties of Zn(II) complexes: Unexpected large TPA cross section of dipolar, Chem. Phys. Lett, vol.3, issue.2, pp.245-249, 2009.
URL : https://hal.archives-ouvertes.fr/hal-00442457

L. Grisanti, C. Sissa, F. Terenziani, A. Painelli, D. Roberto et al., Enhancing the efficiency of two-photon absorption by metal coordination, Phys. Chem. Chem. Phys, vol.11, pp.9450-9457, 2009.

R. M. Edkins, S. L. Bettington, A. E. Goeta, and A. Beeby, Two-photon spectroscopy of cyclometalated iridium complexes, Dalton Trans, vol.40, pp.12765-12770, 2011.

S. W. Botchway, M. Charnley, J. W. Haycock, A. W. Parker, D. L. Rochester et al., Time-resolved and two-photon emission imaging microscopy of live cells with inert platinum complexes, Proc. Natl. Acad. Sci. U. S. A, vol.105, pp.16071-16076, 2008.

M. Sarma, T. Chatterjee, R. Bodapati, K. N. Krishnakanth, S. Hamad et al.,

, 2?-Bipyridine Derivatives as the Ancillary Ligands: Synthesis, Photophysics, and Computational Studies, vol.2, pp.3530-3540, 2016.

K. Kamada, Two-Photon Absorption Spectrum of Non-Centrosymmetric Molecules, Disp. Imag, vol.1, pp.107-130, 2014.

C. Jin, J. Liu, Y. Chen, L. Zeng, R. Guan et al., Cyclometalated Iridium (III) Complexes as Two-Photon Phosphorescent Probes for Specific Mitochondrial Dynamics Tracking in Living Cells, Chem. Eur. J, vol.21, pp.12000-12010, 2015.

G. Li, Q. Lin, L. Sun, C. Feng, P. Zhang et al., A mitochondrial targeted two-photon iridium (III) phosphorescent probe for selective detection of hypochlorite in live cells and in vivo, Biomaterials, vol.53, pp.285-295, 2015.

L. Sun, Y. Chen, S. Kuang, G. Li, R. Guan et al., Iridium (III) anthraquinone complexes as two-photon phosphorescence probes for mitochondria imaging and tracking under hypoxia, Chem. Eur. J, vol.22, pp.8955-8965, 2016.

R. M. Edkins, S. L. Bettington, A. E. Goeta, and A. Beeby, Two-photon spectroscopy of cyclometalated iridium complexes, Dalton Trans, vol.40, pp.12765-12770, 2011.

C. Ho, K. Wong, H. Kong, Y. Ho, C. T. Chan et al., A strong twophoton induced phosphorescent Golgi-specific in vitro marker based on a heteroleptic iridium complex, Chem. Commun, vol.48, pp.2525-2527, 2012.

Y. Fan, D. Ding, and D. Zhao, Two-and three-photon absorption and excitation phosphorescence of oligofluorene-substituted Ir(ppy) 3, Chem. Commun, vol.51, pp.3446-3449, 2015.

L. S. Natrajan, A. Toulmin, A. Chewa, and S. W. Magennis, Two-photon luminescence from polar bis-terpyridyl-stilbene derivatives of Ir(III) and Ru(II), vol.39, pp.10837-10846, 2010.

M. Lepeltier, F. Appaix, Y. Y. Liao, F. Dumur, J. Marrot et al., Carbazole-Substituted Iridium Complex as a Solid State Emitter for Two-Photon Intravital Imaging, Inorg. Chem, vol.55, pp.9586-9595, 2016.
URL : https://hal.archives-ouvertes.fr/hal-01407814