TY - JOUR
T1 - Shortwave infrared luminescent Pt-nanowires
T2 - A mechanistic study of emission in solution and in the solid state
AU - Cheadle, Carl
AU - Ratcliff, Jessica
AU - Berezin, Mikhail
AU - Pal'Shin, Vadim
AU - Nemykin, Victor N.
AU - Gerasimchuk, Nikolay N.
N1 - Funding Information:
NG is very grateful to the following individuals for their help during work on this project: Dr Dan Zhou from the University of Missouri – St Louis for the recording of SEM images; Prof. Dennis Tallman from North Dakota State University for his help with the electrical conductivity measurements of powdery Pt-cyanoximate samples using the AFM method; Dr Allen Oliver (Notre Dame University) and Dr Jeannette Krause (University of Cincinnati) for data collection on the synchrotron source at UC-Berkeley, whereas the Advanced Light Source is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences Division, under contract DE-AC02-05CH11231. Ng is also grateful to Prof. Vlad Kolesnichenko from Xavier University of Louisiana for his initial help with the assessment of particle size in Pt-cyanoxi-mates systems; Prof. Vivian Yam from Hong-Kong University for her help with the initial measurements of photoemission of two Pt-cyanoximates in solutions; Dr Jim Matheis from Horiba for the determination of the NIR emission lifetimes for both Pt-cyanoximates in the solid state; Ms Hanna Roda for her kind help with the electrochemical measurements of the solutions; and Ms Alexandra Corbett for invaluable technical assistance during the manuscript preparation. We also acknowledge MSU Graduate College for partial financial support of this work throughout several years, and the financial support from the NCI/NIH (R21CA149814) and NSF (1355466). We also thank the Washington University Optical Spectroscopy Core Facility (NIH 1S10RR031621-01) for spectroscopy measurements. We are grateful to Dr Justin Douglas from the University of Kansas for recording the EPR spectra of solid samples (support for the EPR instrumentation was provided by NSF Chemical Instrumentation Grant No. 0946883). VNN is grateful for the NSF support with the MRI-1420373 award for acquisition of the mass spectrometer.
Publisher Copyright:
© 2017 The Royal Society of Chemistry.
PY - 2017
Y1 - 2017
N2 - Several complexes of "PtL2" composition containing two cyanoxime anions-2-oximino-2-cyano-N-piperidineacetamide (PiPCO-) and 2-oximino-2-cyano-N-morpholylacetamide (MCO-)-have been obtained and characterized both in solution and in the solid state. Complexes exist as two distinct polymorphs: monomeric yellow complexes and dark-green [PtL2]n 1D polymers, while for the MCO- anion a red, solvent containing dimeric [Pt(MCO)2·DMSO]2 complex has also been isolated. The interconversion of polymorphs was investigated. The monomeric PtL2 units are arranged into anisotropic extended solid [PtL2]n polymers with the help of Pt⋯Pt metallophilic interactions. Crystal structures of monomeric PtL2 (L = PiPCO-, MCO-) and red dimeric [Pt(MCO)2·DMSO]2 complexes were determined and revealed the cis-arrangement of cyanoxime anions. The Pt-Pt distance in the "head-to-tail" red dimer was found to be 3.133 Å. The structure of the polymeric [Pt(PiPCO)2]n compound was elucidated using the EXAFS method and evidenced the formation of Pt-wires with ∼3.15 Å intermetallic separation. The EPR spectra of both 1D polymers at variable temperatures indicate the absence of Pt(iii) species. Both pure dark-green [PtL2]n polymers showed a considerable room temperature electrical conductivity of 20-30 S cm-1, which evidences the formation of a mixed valence Pt(ii)/Pt(iv) system. We discovered that these 1D polymeric [PtL2]n complexes show an intense NIR fluorescence beyond 1000 nm, while yellow monomeric PtL2 complexes are not emissive at all. The room temperature excitation spectra of 1D polymeric [PtL2]n complexes demonstrated their strong emission beyond 1000 nm regardless of the used excitation wavelength between 350 and 800 nm, which is typical of systems with delocalized charge carriers. For the first time the formation of mixed valence "metal wires" held together by metallophilic interactions is directly linked both with an intense fluorescence in the NIR region of the spectrum and with the electrical conductivity. The effect of the concentration of [PtL2]n complexes dispersed in the dielectric salt matrix on the photoluminescence wavelength and intensity was investigated. Both polymers show a quantum yield that is remarkably high for this region of the spectrum, reaching ∼2%. Variable temperature emission of polymeric [PtL2]n in the -190-+60 °C range was studied as well.
AB - Several complexes of "PtL2" composition containing two cyanoxime anions-2-oximino-2-cyano-N-piperidineacetamide (PiPCO-) and 2-oximino-2-cyano-N-morpholylacetamide (MCO-)-have been obtained and characterized both in solution and in the solid state. Complexes exist as two distinct polymorphs: monomeric yellow complexes and dark-green [PtL2]n 1D polymers, while for the MCO- anion a red, solvent containing dimeric [Pt(MCO)2·DMSO]2 complex has also been isolated. The interconversion of polymorphs was investigated. The monomeric PtL2 units are arranged into anisotropic extended solid [PtL2]n polymers with the help of Pt⋯Pt metallophilic interactions. Crystal structures of monomeric PtL2 (L = PiPCO-, MCO-) and red dimeric [Pt(MCO)2·DMSO]2 complexes were determined and revealed the cis-arrangement of cyanoxime anions. The Pt-Pt distance in the "head-to-tail" red dimer was found to be 3.133 Å. The structure of the polymeric [Pt(PiPCO)2]n compound was elucidated using the EXAFS method and evidenced the formation of Pt-wires with ∼3.15 Å intermetallic separation. The EPR spectra of both 1D polymers at variable temperatures indicate the absence of Pt(iii) species. Both pure dark-green [PtL2]n polymers showed a considerable room temperature electrical conductivity of 20-30 S cm-1, which evidences the formation of a mixed valence Pt(ii)/Pt(iv) system. We discovered that these 1D polymeric [PtL2]n complexes show an intense NIR fluorescence beyond 1000 nm, while yellow monomeric PtL2 complexes are not emissive at all. The room temperature excitation spectra of 1D polymeric [PtL2]n complexes demonstrated their strong emission beyond 1000 nm regardless of the used excitation wavelength between 350 and 800 nm, which is typical of systems with delocalized charge carriers. For the first time the formation of mixed valence "metal wires" held together by metallophilic interactions is directly linked both with an intense fluorescence in the NIR region of the spectrum and with the electrical conductivity. The effect of the concentration of [PtL2]n complexes dispersed in the dielectric salt matrix on the photoluminescence wavelength and intensity was investigated. Both polymers show a quantum yield that is remarkably high for this region of the spectrum, reaching ∼2%. Variable temperature emission of polymeric [PtL2]n in the -190-+60 °C range was studied as well.
UR - http://www.scopus.com/inward/record.url?scp=85031129544&partnerID=8YFLogxK
U2 - 10.1039/c7dt02317k
DO - 10.1039/c7dt02317k
M3 - Article
C2 - 28952624
AN - SCOPUS:85031129544
SN - 1477-9226
VL - 46
SP - 13562
EP - 13581
JO - Dalton Transactions
JF - Dalton Transactions
IS - 39
ER -